Alexander’s Distribution of Towns

In a recent post, I analyzed what it would look like to apply the first pattern of Christopher Alexander‘s A Pattern Language to North America. This pattern, titled Independent Regions, created 50 new, small nations or regions within what is today the United States and Canada. The next thing I wanted to try was applying Alexander’s second pattern, The Distribution of Towns, to one of those new regions. The pattern reads:

If the population of a region is weighted too far toward small villages, modern civilization can never emerge; but if the population is weighted too far toward big cities, the earth will go to ruin because the population isn’t where it needs to be, to take care of it.


Encourage a birth and death process for towns within the region, which gradually has these effects:
1. The population is evenly distributed in terms of different sizes- example, one town with 1,000,000 people, 10 towns with 100,000 people each, 100 towns with 10,000 people each, and 1000 towns with 1000 people each.
2. These towns are distributed in space in such a way that within each size category the towns are homogeneously distributed all across the region.

This process can be implemented by regional zoning policies, land grants, and incentives which encourage industries to locate according to the dictates of the distribution.

apl2diagramtowns of 1,000,000 – 250 miles apart
towns of 100,000 – 80 miles apart
towns of 10,000 – 25 miles apart
towns of 1,000 – 8 miles apart

However, as discussed in the previous post, not all regions that meet Alexander’s population criteria automatically meet his spacing criteria when you move from Pattern 1 to Pattern 2. Several regions are too large and sparse, while several more are too small and dense.

Click to enlarge.

Click to enlarge.

So to analyze Pattern 2 without worrying about redistributing the population of the regions until they were the right size, I wanted to pick one of the “Goldilocks” regions that is already about the right size. I went with the Washington DC Region.

Click to enlarge.

Click to enlarge.

Now for the distribution part. Let’s say that we have a region, Region A, with capital city City 1 in its center.Diagram1-01Alexander recommends one very large city per region, so we’ll assume that City 1 has a population of about a million and that it’s the only city of it’s scale in the region. Our first step is to identify our cities of 100,000 people. While Alexander recommended making these cities 80 miles apart, I used 72 miles to simplify the math a little bit. So we want to make sure that these cities of 100,000 are 72 miles from City 1, as well as from each other.Diagram2-01Next we want to identify our towns of 10,000. Again, I fudged Alexander’s math a bit, and identified towns that are 24 miles (1/3 of 72) from any larger cities or from each other.Diagram3-01And finally, we want to identify towns of 1,000 people, eight miles from any larger town and from each other.Diagram4-01That’s what it looks like in an ideal world. However, in the real world, we’re not starting with a blank slate, and rather than founding new cities that are perfectly spaced from DC, I wanted to identify existing cities located in the right place. When you do that, it looks like this:

Click to enlarge.

Click to enlarge.

What this technique doesn’t consider, however, is why cities are located where they are: largely, access to resources, and access to transportation. They aren’t distributed evenly across a landscape; they’re bunched up in the places that have access to mineral, agricultural or intellectual wealth, and places that have access to ports, railroads, and highways. Disregarding this truth about cities means that some cities that are not located the right distance away from one another can get hosed. Case in point, Richmond, a city of over 200,000 people at the center of a metro area with over 1.2 million, because it isn’t spaced correctly relative to DC, is relegated to the 10,000 people tier, meaning that a huge population would be resettled to areas like Tappahannock (current population 2,397) or Powhatan (current population 49) which are spaced correctly.

Also, by using Alexander’s spacing suggestions, one does not arrive at his suggestion for how many towns there should be. Based on this distribution, you end up with one town of 1,000,000, eight towns of 100,000, 45 towns of 10,000, and 319 towns of 1,000. That adds up to 2,569,000 people. But in the last pattern, we determined that the Washington DC Region would have a population of 8,917,843. So where are the other 6 million plus people living?

The answer to that actually comes from another pattern, number 5 in Alexander’s book, Lace of Country Streets:

The suburb is an obsolete and contradictory form of human settlement.


In the zone where city and country meet, place country roads at least a mile apart, so that they enclose squares of countryside and farmland at least one square mile in area. Build homesteads along these roads, one lot deep, on lots of at least half an acre, with the square mile of open countryside or farmland behind the houses.

Alexander doesn’t specify how wide this “zone where city and country meet” is, and if we’re got small cities every eight miles across an entire region, it would almost follow that these zones fill in the rest of the space between towns. If we take a square mile, and line it on all four sides with lots that are just over a half acre, we come up with 116 lots per square mile. If we multiply that by the average household size in the US of 2.58 persons per household, we get about 300 people per square mile in the countryside. If you multiply that by the 24,945 square miles covered by our region, you get 7,483,500 people. If you remove some to consider that a considerable portion of our region is the Chesapeake Bay and that some of those 24,945 square miles are already taken up by towns and, therefore, the Lace of Country Streets wouldn’t apply, it basically adds up to the rest of the people we were looking for.

So what we end up with is a pretty even population distribution across the entire region with a bit more concentrated in the many small towns and a lot more concentrated in the few big cities. but is this even distribution good for people or for the environment? I take issue with part of Alexander’s rationale for this pattern:

Two different necessities govern the distribution of population in a region. On the one hand, people are drawn to cities: they are drawn by the growth of civilization, jobs, education, economic growth, information. On the other hand, the region as a social and ecological whole will not be properly maintained unless the people of the region are fairly well spread out across it, living in many different kinds of settlements – farms, villages, towns, and cities – with each settlement taking care of the land around it. Industrial society has so far been following only the first of these necessities. People leave the farms and towns and villages and pack into the cities, leaving vast parts of the region depopulated and undermaintained.

But what does it mean to “take care of” and “maintain” the countryside? It seems to me that the countryside does pretty well without us up in its business. Alexander mentions the ecology of the city and how large cities are bad ecologically, but (a) some of Alexander’s patterns that I will discuss later address that and (b) by pulling people away from the countryside and concentrating them in cities, it allows for the countryside to function as what we need it most for (a carbon sink), and allows people to take advantage of shared walls and transit systems which greatly reduce our per-capita carbon footprint. If it were me, I’d distribute the population more like this:

Click to enlarge.

Click to enlarge.

Making all the big cities even bigger and, most importantly, denser, and leaving only small villages sprinkled throughout the countryside. As long as enough people live out there to grow the food and operate the mines for everyone else, there’s no reason to have everyone flung out across the landscape. The best thing we can do for the countryside really is to leave it alone. As far as getting people access to natural environments, we’ll talk about that soon, when I take a look at Alexander’s 3rd pattern, City Country Fingers.

Best Country in the World: Professional Networking Edition

After I wrote my last post about which countries are the best in the world and three of the top five were in Scandinavia, I got curious about what it might take to move there. From my quick research, it seems that in all the Scandinavian countries, if you want to get a job, you need to (a) speak the language (working on it) and (b) know someone, because companies want to hire natives before they want to try and bring someone in from another country (or at least a country outside of Europe). So I was curious who I might know in Scandinavia, and if that could again help me focus on one language to learn instead of three. Of course I don’t know anyone off the top of my head, but I knew a way to find people I know who might themselves know someone: LinkedIn.

LinkedIn allows you to do a fairly precise search for contacts, including location, industry, and how well you know someone (1st, 2nd, or 3rd-level contact, it’s kind of like Six Degrees of Kevin Bacon). So I searched for 2nd-level contacts living in Denmark, Norway and Sweden, and in the fields of architecture and planning, research, government administration, and non-profits.

I got about 99 results, although I could only look at about 70 of them before hitting LinkedIn’s commercial search limit (not cool, LinkedIn). I then mapped them out, marking how well their field of work matches my interests, and how well I know our mutual contact, since I have several people on my LinkedIn that I’ve met once or have only corresponded with via email.Map-01I have four cities with a decent number of contacts: Copenhagen (København), Oslo, Stockholm, and Trondheim. Of those, the most contacts in a related field are in Copenhagen and Stockholm. But the highest quality contacts, those where I actually know our mutual contact well, are in Copenhagen. So maybe, for now, I’ll focus on learning Danish.

Finding the Best Country in the World

I’m a bit paranoid. Like when I get home, stick my head in the door, look around, and tell my wife, “Yep, no racoons,” I’m only sort of kidding (a racoon did break into my house when I was a kid so that’s not a totally crazy thing to say). One way this paranoia manifests itself is in creating certain contingency plans. For instance, if I had to flee the country where would I go? The easy answer would be the other English-speaking countries (Canada first because it’s close, the UK second because it’s further but I have friends there, New Zealand third because it looked nice in Lord of the Rings and Australia last because I’m sorry but I do not trust your fauna). But what if, say, all the English speaking countries got nuked or something? Or if we find out that global warming only affects them and they get wiped off the face of the earth? Or they all get conquered by North Korea? Well, if that’s the case, it’s time to flee to a non-English speaking country and learn another language. But which one?

At one point I couldn’t decide, and I was studying Danish, Dutch, Irish, Spanish and Swedish on Duolingo all at the same time (yes, I know next to no one speaks Irish, that was just for kicks). Eventually I cut out Irish and Spanish, but also picked up German, so I wasn’t much better off. So I wanted to figure out, if I’m going to have to flee to another country, including non-English speaking countries, which ones should I focus on so that I can actually study their language effectively?

I thought the Human Development Index (HDI) was a good place to start. It measures a country’s well-being based on a combination of several factors, including life expectancy, education and income. Its top five countries are Norway, Australia, Switzerland, the Netherlands, and the United States. However, HDI doesn’t measure everything. In fact, in 2010 they introduced a new index, the Inequality-Adjusted Human Development Index (IHDI) to try and fill in some of the gaps. This new adjustment changes the top five to Norway, Australia, the Netherlands, Switzerland, and Germany, and kicked the US down to 28th, three spots below Greece.

My thought was that the best way to cover as many factors as I could was to combine as many different indices as I could to create one super index that would bring in enough factors to create a truly well-rounded indicator of what the best country was. I combined the IHDI, Democracy Index, Human Poverty Index, Social Progress Index, World Happiness Report, Global Peace Index, Legatum Prosperity Index, Where-to-be-born Index, Satisfaction with Life Index, and OECD Better Life Index to create what I call the Best Country Index.

Index Index2

So the top five are Norway, Sweden, Switzerland, Denmark, and Finland. Well, right now Norwegian isn’t offered on Duolingo, so even if it’s number one I’m not studying it until they finish creating the course for it, so for now I’ll just have to assume it’s somewhere between Danish and Swedish. And I’m not even going to try with Finnish; I had a hard enough time with Irish, and that’s still an Indo-European language, I can only imagine the sort of trouble I would have learning a Finno-Ugric one. So that leaves me (until Duolingo adds Norwegian) with Swedish, German, and Danish. Well, at least I can stop studying Dutch for now.

For those of you who would like a searchable version of the list above, here it is:

  1. Norway, 2.9877
  2. Sweden, 2.9732
  3. Switzerland, 2.9724
  4. Denmark, 2.9702
  5. Finland, 2.8872
  6. Canada, 2.8858
  7. Netherlands, 2.8778
  8. Australia, 2.8257
  9. New Zealand, 2.7938
  10. Austria, 2.7792
  11. Germany, 2.6754
  12. Ireland, 2.6643
  13. Iceland, 2.6580
  14. Belgium, 2.5993
  15. United Kingdom, 2.4850
  16. United States, 2.4315
  17. France, 2.3879
  18. Japan, 2.3759
  19. Spain, 2.3667
  20. Slovenia, 2.2898
  21. Czech Republic, 2.2789
  22. Italy, 2.2484
  23. Costa Rica, 2.2419
  24. Chile, 2.1414
  25. Luxembourg, 2.1216
  26. South Korea, 2.1083
  27. Singapore, 2.0700
  28. Poland, 2.0554
  29. Slovakia, 2.0191
  30. Portugal, 2.0180
  31. Israel, 2.0131
  32. United Arab Emirates, 1.9953
  33. Argentina, 1.9745
  34. Uruguay, 1.9719
  35. Kuwait, 1.9342
  36. Cyprus, 1.9248
  37. Panama, 1.9047
  38. Estonia, 1.8984
  39. Hungary, 1.8743
  40. Croatia, 1.8356
  41. Malaysia, 1.8159
  42. Taiwan, 1.8096
  43. Malta, 1.8054
  44. Greece, 1.7843
  45. Brazil, 1.7838
  46. Trinidad and Tobago, 1.7417
  47. Mauritius, 1.7076
  48. Hong Kong, 1.7074
  49. Mexico, 1.6853
  50. Latvia, 1.6692
  51. Lithuania, 1.6575
  52. Saudi Arabia, 1.6445
  53. Colombia, 1.5608
  54. Romania, 1.5560
  55. Bulgaria, 1.5293
  56. Mongolia, 1.5285
  57. Jamaica, 1.5272
  58. Venezuela, 1.5111
  59. Serbia, 1.4994
  60. Dominican Republic, 1.4682
  61. Thailand, 1.4682
  62. Qatar, 1.4612
  63. Indonesia, 1.4586
  64. Ecuador, 1.3933
  65. Montenegro, 1.3921
  66. Paraguay, 1.3908
  67. Botswana, 1.3800
  68. Peru, 1.3728
  69. El Salvador, 1.3698
  70. Brunei, 1.3360
  71. Bhutan, 1.3356
  72. Philippines, 1.3135
  73. Bahamas, 1.2969
  74. Suriname, 1.2959
  75. Nicaragua, 1.2713
  76. Guatemala, 1.2650
  77. Sri Lanka, 1.2616
  78. Albania, 1.2463
  79. Vietnam, 1.2340
  80. Macedonia, 1.2286
  81. Cuba, 1.2284
  82. Guyana, 1.2281
  83. Bolivia, 1.2224
  84. Namibia, 1.2217
  85. Kazakhstan, 1.2140
  86. Tunisia, 1.2068
  87. Bosnia and Herzegovina, 1.1818
  88. Oman, 1.1790
  89. Turkey, 1.1783
  90. South Africa, 1.1738
  91. Antigua and Barbuda, 1.1625
  92. Belarus, 1.1555
  93. Jordan, 1.1534
  94. East Timor, 1.1433
  95. Moldova, 1.1385
  96. Seychelles, 1.1310
  97. St. Kitts and Nevis, 1.1231
  98. Honduras, 1.1190
  99. Ghana, 1.1158
  100. Liechtenstein, 1.1140
  101. Uzbekistan, 1.0997
  102. Vanuatu, 1.0995
  103. Barbados, 1.0759
  104. Kyrgyzstan, 1.0725
  105. Dominica, 1.0601
  106. Morocco, 1.0518
  107. Belize, 1.0164
  108. Fiji, 1.0143
  109. Ukraine, 1.0137
  110. China, 1.0126
  111. Georgia, 1.0109
  112. Bahrain, 0.9991
  113. Cape Verde, 0.9768
  114. St. Vincent and the Grenadines, 0.9734
  115. Russia, 0.9629
  116. Andorra, 0.9617
  117. India, 0.9617
  118. Armenia, 0.9466
  119. Bangladesh, 0.9446
  120. Zambia, 0.9422
  121. Senegal, 0.9332
  122. Azerbaijan, 0.9238
  123. St. Lucia, 0.9183
  124. Lebanon, 0.8938
  125. Gabon, 0.8898
  126. Nepal, 0.8886
  127. Samoa, 0.8789
  128. Papua New Guinea, 0.8788
  129. Tanzania, 0.8685
  130. Algeria, 0.8633
  131. Cambodia, 0.8305
  132. Maldives, 0.8239
  133. Lesotho, 0.8086
  134. Iran, 0.8053
  135. Laos, 0.7953
  136. Madagascar, 0.7853
  137. Kenya, 0.7636
  138. Benin, 0.7603
  139. Tajikistan, 0.7579
  140. Solomon Islands, 0.7452
  141. Tonga, 0.7371
  142. Sao Tome and Principe, 0.7316
  143. Grenada, 0.7213
  144. Egypt, 0.7050
  145. Palestine, 0.6883
  146. Malawi, 0.6800
  147. Mozambique, 0.6666
  148. Burkina Faso, 0.6468
  149. Congo, 0.6432
  150. Uganda, 0.6267
  151. Mali, 0.6129
  152. Angola, 0.6028
  153. Liberia, 0.5733
  154. Sierra Leone, 0.5716
  155. Libya, 0.5652
  156. Cameroon, 0.5604
  157. Haiti, 0.5543
  158. Gambia, 0.5511
  159. Djibouti, 0.5483
  160. Mauritania, 0.5472
  161. Nigeria, 0.5384
  162. Togo, 0.5369
  163. Swaziland, 0.5051
  164. Pakistan, 0.5007
  165. Rwanda, 0.4921
  166. Comoros, 0.4904
  167. Iraq, 0.4849
  168. Yemen, 0.4505
  169. Kiribati, 0.4407
  170. Turkmenistan, 0.4333
  171. Niger, 0.4307
  172. Syria, 0.4233
  173. Guinea, 0.3683
  174. Ethiopia, 0.3662
  175. Equatorial Guinea, 0.3662
  176. Cote d’Ivoire, 0.3357
  177. Burma, 0.3104
  178. Zimbabwe, 0.2542
  179. Burundi, 0.2502
  180. Guinea-Bissau, 0.2489
  181. Eritrea, 0.1878
  182. Afghanistan, 0.1861
  183. Central African Republic, 0.1709
  184. Chad, 0.1657
  185. Sudan, 0.1458
  186. Democratic Republic of the Congo, 0.0675
  187. Somalia, 0.0205
  188. North Korea, 0.0169 My New Favorite Website

A short one today, but I really wanted to mention a new website I found called Streetmix. It allows you to create street cross sections on the fly, with different options for buildings, sidewalk elements, and travel lanes. For instance, in less than a half hour, I made five different cross sections for different parts of Columbia Pike, a major thoroughfare in Arlington, Virginia. The eastern section of the road has a lot of Modernist housing blocks that are tall and set way back from the street:columbia-pike-at-scott-stBut further west, it has more of a Main Street feel, with tall buildings coming right up to wider sidewalks:columbia-pike-at-walter-reed-drUp until very recently there were plans to put a streetcar line in on Columbia Pike, which were defeated by a zealot who convinced people that a BRT would be cheaper (which it wouldn’t be) and politically feasible (which it isn’t because it would take away a travel lane in each direction and the turn lane, which Arlington isn’t allowed to do as per an agreement with the Commonwealth). Here’s what this section would look like with a streetcar (note that the streetcar lanes are not dedicated and would still allow car traffic):columbia-pike-at-walter-reed-dr-with-streetcarAnd with BRT:columbia-pike-at-walter-reed-dr-with-brtFinally, as Columbia Pike heads further west and into the Bailey’s Crossroads area of Fairfax County, it widens into a strip mall super street:columbia-pike-at-moray-lnAll of this is to say that Streetmix makes it easy to create and compare cross sections of streets on the fly. While I wouldn’t use it for final documents, it gives you something to play around with and to work off of. And for planning nerds like me, it’s just a lot of fun.

A Study on Regional Governments Part III: Back to North America

I’ve been working on regional governments on and off for several years, and this time I feel like I’ve made some progress. There are a number of reasons for subdividing North America into new regional governments, as I’ve already discussed in Part I and Part II. But the main idea comes from architect and known crazy person Christopher Alexander‘s book A Pattern Language, a book about development and building patterns that goes from the very large to the very small scale. The very first pattern in the book is:

Metropolitan regions will not come to balance until each one is small and autonomous enough to be an independent sphere of culture…


Wherever possible, work toward the evolution of independent regions in the world; each with a population between 2 and 10 million; each with its own natural and geographic boundaries; each with its own economy; each one autonomous and self-governing; each with a seat in a world government, without the intervening power of larger states or countries.

This time I tried to be more official and used a GIS to do my work rather than Google and Wikipedia. In the past I’ve used counties as my basic geographic and population unit, but that was problematic, seeing as Los Angeles County has over 10 million people already. It’s also problematic to go down to the level of cities, towns and places, because then you run into 8 million-strong New York City, and the second you lump in any of its suburbs it puts you over 10 million. This time I went in between and used county subdivisions, which will both divide Los Angeles County up as well as take advantage of the fact that New York City, while being one city, is also five different counties.

I also used information from both the US and Canada. Initially I wanted to do Mexico as well, since there are a number of major cities on the Mexican side of the border that draw people in from the US. However, I figure that the ties between the US and Canada are much stronger and that it would be easier to integrate their populations. Also, the fact that the US and Canada make census data and GIS files fairly easy to obtain while Mexico doesn’t might have something to do with it.

My methodology goes something like this. Let’s say you’ve got Country A with Cities 1, 2, and 3 and a population of 30 million.

Process1City 1 and City 2 are the largest cities in the country, so the country would be divided between these two cities.Process2Region 1’s new population is 18 million and Region 2’s is 12 million. Since Region 1 is the larger of the two and since it is still above 10 million in population, it needs to be divided again. The second largest city in Region 2 is City 3, so new boundaries need to be redrawn between that and the two existing cities.Process3The new Region 3 took 8 million people from Region 1 and 2 million from Region 2, giving all three regions a nice round population of 10 million. At this point we no longer need to subdivide them any further.

Of course, when you do this on real land and using real borders, it doesn’t come out quite as clean. It looks a bit more like this:

Click to enlarge.

Click to enlarge.

TableThe largest metropolitan area in Anglo-America is New York City and the second is Los Angeles, so they became the first two regions. Since they were both over 10 million and New York City was the larger of the two, Chicago was the third region, then Dallas, then Philadelphia, etc.

What is apparent in this exercise is that, since the regions are based on population and not geography, the size of the region correlates to population density. The densest parts of Anglo-America, the northeast seaboard and southern California, have the smallest regions, while the sparsely populated Rocky Mountains and northern Canada have enormous regions. What I haven’t realized in past iterations of this project is that it complicates Alexander’s second pattern, the distribution of towns:

If the population of a region is weighted too far toward small villages, modern civilization can never emerge; but if the population is weighted too far toward big cities, the earth will go to ruin because the population isn’t where it needs to be, to take care of it.


Encourage a birth and death process for towns within the region, which gradually has these effects:
1. The population is evenly distributed in terms of different sizes- example, one town with 1,000,000 people, 10 towns with 100,000 people each, 100 towns with 10,000 people each, and 1000 towns with 1000 people each.
2. These towns are distributed in space in such a way that within each size category the towns are homogeneously distributed all across the region.

This process can be implemented by regional zoning policies, land grants, and incentives which encourage industries to locate according to the dictates of the distribution.

apl2diagramtowns of 1,000,000 – 250 miles apart
towns of 100,000 – 80 miles apart
towns of 10,000 – 25 miles apart
towns of 1,000 – 8 miles apart

The last part of that section, which describes the spacing of towns, leads to a specific size that a nation of a given population should be. I experimented with a few town distribution models and determined that based on a combination of Alexander’s population and town distribution recommendations, a region should not be less than approximately 30,000 square miles, without being more than approximately 130,000 square miles. Several of the regions I’ve created based on population alone are either too large or too small to meet these criteria.

Click to enlarge.

Click to enlarge.

So to comply with Alexander’s recommendations, the small regions would have to have their population distributed more sparsely and their boundaries enlarged to accommodate that lower density, and the large regions would either have to become smaller and more dense, or have their populations concentrated in certain areas while others are left as uninhabited wastes, as is essentially the case in much of the mountain deserts of the western US and the arctic regions of Canada.

While I see the value of Alexander’s argument for smaller governmental units, I find his arguments for the distribution of towns a bit more dubious, especially when it comes to areas that are too dense for his recommendations. I generally feel that the best way to preserve undeveloped land is not to distribute people evenly across it, but to concentrate them all in one area and leave more of the land untouched. That’s why New Yorkers are some of the greenest people on earth; they leave the countryside alone, and are packed dense enough that they don’t have to use cars and take advantage of the energy savings of dense housing, making their environmental impact considerably lower than someone in a lower density area.

That being said, at some point I would like to take one of the Goldilocks regions I’ve created like San Francisco or Pittsburgh and try to create a distribution of towns like what Alexander recommends, just to see what it would look like. But as far as drawing new regions goes, I’m pretty happy with this version, and I don’t see myself redoing this project again.

Where can I find a decent townhouse?

I live in an apartment. And that works for a lot of people – limited maintenance, the flexibility to move more easily, the lower carbon footprint, the often greater access to urban amenities and transit – all good things. But I don’t want to live in an apartment long term. I want to own my own place, and not have to worry so much about noisy neighbors. So am I looking for a single-family home in the suburbs? If you’ve ever read this blog at all, you know that’s not the case.

I want a townhouse. For me, it seems to be the best of both worlds. It provides for owner-occupied housing without the associations and fees of condos. It eliminates upstairs and downstairs neighbors altogether, and thicker walls better insulate from sounds next door. Yet it is still an urban form of housing which takes up less space than a suburban single-family home, and requires less maintenance (because, let’s be honest, I never want to mow a lawn again in my life if I can avoid it, that’s what the Parks Department is for).

In Census terms, a townhouse is an attached single-family home (in that it is owner occupied, but immediately adjacent to other units), and in much of the US, anything that meets that definition is called a townhouse. But I lived in Philadelphia for four years, and as a city full of single-family attached homes, the residents there make distinctions within that definition. Here are some of the types of single-family attached units.

The True Townhouse

Townhouses in Gdansk, Poland. From Wikipedia.

True townhouses are built individually, one by one, and are distinct from the other townhouses on the street. They have “sandwich walls,” meaning that the adjacent buildings don’t share a wall between them, but have separate walls built right next to each other, which provides for excellent sound insulation. As many of these are essentially custom built, they have historically been associated with the upper classes. The “Brownstones” of various cities on the East Coast are part of this group.

The Rowhouse

Rowhouses in Leeds, UK. From Wikipedia.

Rowhouses (terraced houses for the British types), on the other hand, are usually mass-produced and have similar, if not identical, appearances. They have “shared” or “party walls” between them and often share the same roof line, unless they are in a particularly hilly area. Because they were mass-produced, they are more often associated with the middle- and lower-classes, and with industrial cities where housing was needed for their swelling populations.

The Twin House

Twin houses in Philadelphia. From

As far as I can tell, the name “twin house” is sort of a Philadelphia thing. In other places they might be called duplexes or semi-detached houses. A twin house is basically a set of just two rowhouses with a gap on either side. This allows for a little more space and privacy while still preserving the density of the houses listed above. The floorplans of the houses are usually mirror images of each other, and they may have similar exterior features, although in Philadelphia it is fairly common for neighboring twin homes to use distinct trim colors or small architectural accents. Twins (or semis, as they are more likely to be called there) are the most common dwelling type in England.

For me, all of these dwelling types are great. They are owner-occupied and have enough space for a family while still being low-maintenance and urban. However, if you look on Zillow or other real estate websites for townhouses, you’re also going to get a lot of junk, like:

Patio Homes

From Wikipedia.

Patio homes have shared walls, so you can hear the noise of your neighbors. They are set in extensive grounds that are often maintained by a home owners or condo association. They are often located in suburban or exurban communities. Therefore, they have all the disadvantages of rowhouses, condos, and single-family homes, all in one inconvenient bundle.

Two Suburban Houses Stuck Together


Is there really any advantage to this housing type? At least with the patio home (which often has some overlap with this one), they’re usually in a pleasant, albeit remote, location, and you have someone else doing your maintenance, even though you have to relinquish some decision making power to the association. But where I’ve seen these has mostly been in bland, undesirable suburbs, and you have to do your own yardwork. Are they really so affordable that there is any benefit to them over just going all the way for a suburban house?

Attached Garages with Houses Hiding Behind Them


I feel like I’ve seen more of this housing type in the west, and particularly on military bases. It sort of assumes that streets are for cars and no one is ever going to walk to this place, so why even pretend that a front door is something someone would need to see from the street. All the problems of density without the advantages of urbanity.

Add to that the fact that some real estate agents seem to think that “townhouse” just means “small house” and you have a lot to weed through when looking for a townhouse. I should know, because I weeded through all of it.

I went on Zillow and searched for my dream house (townhouse, three bedrooms, two baths, under $300,000, with a Walk Score over 70) in every state. Here’s what that looks like:

Townhouses-01There are various reasons why a state would have a low score. Some just aren’t very walkable (Texas, Maine). Some aren’t very affordable (California, Massachusetts). Others just don’t have a lot of townhouses. But what I found really interesting was that there is a corridor, running roughly from Trenton, through Philadelphia and Wilmington and to Baltimore, where there were just tons of affordable, walkable townhouses.

These cities are walkable because they are old, traditional cities that were built at the scale of the pedestrian; and they are affordable partially because they have a large supply of housing, and because the demand isn’t as high as some neighboring markets like in Washington and New York. My question was, why is the supply so high here, and not even in nearby places like Pittsburgh?

That question largely comes down to history. The Trenton-Baltimore corridor was one of the earliest parts of the country to industrialize. Like the cities in the north of England, their housing was built quickly to serve an enormous influx of new residents coming from the countryside or other countries for jobs, which is why both of these areas have a lot of rowhouses. Pittsburgh, although it is known as a major industrial center, developed just a little bit later, after the rowhouse had gone out of style as it was associated with tenements and poor working conditions. While Philadelphia is a city of rowhouses, Pittsburgh is a city of small, narrow, vertically-oriented single family homes. It’s like you took Philadelphia, put a couple of feet between each rowhouse, threw in some crazy topography, and that’s how you make Pittsburgh. Even though they are technically not townhouses, the homes of Pittsburgh are similarly urban, efficient, and low-maintenance.

Pittsburgh. From

So, could I live in a single-family home? I guess, as long as it functions like a townhouse. As long as it’s in a neighborhood where I can walk to services, where I’m not bound by a condo association, and where I don’t have to mow a lawn because there’s a decent park nearby, it works for me.

How Cities have been Shaped by Defense

So in your spare time you’re looking at an aerial view of London on your favorite online mapping service (as one does), when you notice a street called London Wall.

London 2

And as you’re looking at your map, you notice other wall-y things, like Old Bailey and Houndsditch.London 3And then you notice that perpendicular to these wall-y things are lots of gate-y things: Ludgate Hill, Newgate, Moorgate, Bishopsgate, Aldgate.

London 4And at about this point you start to see a shape and realize,London 5You can learn a lot about a city’s history by looking at a map of it. If you know what to look for, you can see how high places, walls, and other fortifications had a major effect in shaping our cities.

Early settlements all around the world were formed on the tops of hills. Hills are naturally defensible, because they allow you to see a greater distance and force your enemy to expend energy getting up the hill. Even in the large, flat expanses of the Levant, cities would create the advantages found on the more natural hill forts of Europe by building giant piles of dirt, or tells.

Tell Barri in Syria. From

It wasn’t a stretch to get from “let’s build our city on this hill” to “this hill would be really great with a wall around it.” And thus, the citadel was born.

Citadel of Arbil in Iraq. From

The citadel, of course, had different regional names, including the acropolis and the oppidum. Initially they were built of whatever was available, be it stone, wood, mud brick, or rammed earth. But in most places, stone or masonry eventually prevailed.

Groß Raden Archaeological Open Air Museum in Germany. From

In many cities, the fortified citadel grew to house only the city’s political and/or religious elite, while the normal residents were outside of the walls and subject to attack. But eventually the rulers decided that it was worthwhile to defend their soldiers, scholars and artisans, and cities began erecting full perimeter walls.

The weapons these walls were built to defend from were mostly just guys with swords, arrows, and in some cases fairly light siege equipment. As such, they didn’t need to be particularly thick, but they did need to be high. These walls often followed contours and were somewhat organic. They had fairly regularly spaced towers from which to shoot arrows or throw rocks, and were usually the joints at which straight walls would change direction.

The walls and towers of Rothenburg ob der Tauber, Germany. From

More importantly for urban design, the city wall provided a natural growth boundary. Especially during the uncertain times of the European Dark Ages and the invasions of the Germans, Huns, Slavs, Vikings, Arabs and Mongols (that’s everyone who invaded anything between the end of the Roman Empire and the introduction of the cannon, right? You get my point), there was a huge incentive to be inside the city walls rather than unprotected in the fields or the lawless countryside. The European feudal system only added fuel to the urban fire; peasants and slaves alike would flee to cities to escape their masters. In Germany, the law was that a serf was a free citizen of a city after a year and a day, thus the phrase Stadtluft macht frei nach Jahr und Tag (“city air makes you free after a year and a day”), better known for its shorthand, Stadtluft macht frei (“city air makes you free”).

The end of this phase of wall building came with the cannon. Unlike previous siege engines like the catapult and trebuchet, which threw objects over city walls to cause damage within, the cannon, with just a few direct hits, could pierce a wall, allowing for foot soldiers to enter the city. The vertical wall laid out perpendicular to the enemy allowed the cannon ball to focus all of its energy on one point, causing maximum destruction. The solution was to not try to necessarily stop the ball, but to diminish its destructive power by deflecting it. And thus the star-shaped wall was born.

These walls were not vertical and not perpendicular, but formed a jagged, pointed wall that sloped back toward the city. The angled and sloped walls, which were also much thicker, made it more likely that a cannon ball would simply bounce off and roll away harmlessly. The star points on the walls also allowed soldiers a forward position from which to attack the enemy, with the civilian population located further back from the action.

Naarden, the Netherlands. From

Star-shaped walls were massive feats of engineering, and only the wealthiest cities could fully enclose themselves within them. Some cities would create small forward military towns which would be heavily fortified, such as Palmanova outside of Venice. But in many cities would simply build a star-walled fort at a strategic location, such as the confluence of two rivers (Fort Pitt at Pittsburgh) or on the harbor (Fort McHenry at Baltimore).

Fort McHenry guarding Baltimore Harbor. From

There aren’t many cities whose star-shapped walls or forts remain. That is because they take up a huge amount of land, and as many cities, particularly in the west, began to feel less threatened by foreign armies, they wanted to use that land for other purposes. Many of these areas were redeveloped for public use. For instance, the former site of Fort Pitt in Pittsburgh is now Point State Park, where only traces of the former fort (as well as its French predecessor, Fort Duquesne) remain.

The outlines of Fort Duquesne (smaller, left) and Fort Pitt (larger, right) at Point State Park, Pittsburgh. From Google Earth.

The outlines of Fort Duquesne (smaller, left) and Fort Pitt (larger, right) at Point State Park, Pittsburgh. From Google Earth.

One famous example of a star-walled ring being replaced is the Ringstraße in Vienna. In the 1800s, Vienna had a star wall around its old quarter, but new districts had sprung up on the outside of the wall, and completely encircled it. Vienna was essentially the hole in a fortified doughnut. In the 1860s, the city chose to tear down its old fortifications, replacing them with a ring road, public parks, and major public buildings.

Ringstraße, before and after the redevelopment of the fortifications. From

It was about this time that explosive artillery shells were introduced, which star-shaped fortifications did not perform well against. These weapons also lead to the end of urban fortifications. The radius of damage from explosive shells was just too large for cities to feel comfortable going against, and the defense of cities fell to rings or lines of polygonal forts set back about eight miles from the city. Yet even without the enclosing walls, there was still an incentive to be in the city, where you were protected by the ring of forts, rather than in suburbs of the open countryside. That incentive came later, with the introduction of aerial bombardment and, later, nuclear weapons.

The nuclear era was the first time that the incentive for defense actually pushed people out of cities. When you have a single weapon that can kill hundreds of thousands in an instant and level an entire city, urban areas start to look less like refuges and more like targets. While there were many factors that led to suburbanization in America, the fear of a Soviet nuclear attack cannot be overlooked. One of the many reasons the interstate highway system was built was so that cities could be evacuated in case of an emergency, and one could imagine that those who fled for the suburbs were simply planning ahead.

That being said, there have been several proposals and even a few attempts at creating urban defenses in the nuclear age. There were many proposals for domed cities a la Buckminster Fuller, although his domes were largely meant as a means to prevent air pollution and provide city-wide climate control. The Underground City of Beijing, built during a spat with the Soviets in the 70s, was a network of underground tunnels, featuring shops, warehouses, and even mushroom farms (since mushrooms can grow without light), and supposedly could have held all of Beijing’s population of 6 million at the time. Switzerland, which is just chock full of air raid shelters, intended a double use for the Sonnenberg Tunnel outside of Lucerne, which would have been able to house 20,000 people in the event of a nuclear attack.

Buckminster Fuller’s Midtown Manhattan Dome. From

I think part of the reason that my generation is returning to the city, although it may not be a conscious factor, is that the Cold War is over, and there really isn’t a world power out there with the air force and nuclear capabilities to attack us the way the Soviets could have. While it may have been a perfectly reasonable fear of nuclear annihilation that encouraged our parents or grandparents to leave cities, we don’t have that same fear. The greatest outside threat to our safety is no longer a State with official armed forces, but the small, loosely organized groups and individuals that today are the perpetrators of terrorism. But with few exceptions, terrorists cannot attack a large area at once, and although cities do employ counterterrorism measures, the targets of terrorism aren’t cities, they are usually individual properties or persons. That is why today we are seeing a resurgence of defensive construction, not on the city scale, but on the scale of the individual building.

Bollards, bollards everywhere at HHS in Washington, DC. From

Bollards, bollards everywhere at HHS in Washington, DC. From

While defense no longer encourages us to move to cities as it once did, it allows us to, more than it may have our parents or grandparents. The technology of war, as well as its general presence, may continue to be a factor in how we design our cities in the future, but the city of today is a safe place, and getting safer. As Stephen Pinker points out in The Better Angels of our Nature, violence in the world is on the decline, both on the scales of the individual and the nation state. With less to fear, we may be more able to enjoy the benefits that the city has to offer us.

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