Why are blocks that size?

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Why are blocks that size?

by Erik Bootsma • June 2, 2010 2:04 pm

Daniel Nairn posted an interesting comparison of the street grids in various cities in the United States. This raised the question: why did various cities choose one block size over another?

Poster by Daniel Nairn.

Why, for instance, are the blocks in Tuscon, Arizona 400 feet on a side, while Portland, Oregon has 200-foot blocks?

The block sizes of most cities stem from the interaction of architecture and nature. Local climatic conditions affect the shape of a building and its lot.

In the north, the climate is primarily cold and dark, and in the south it's hot and sunny. This is more pronounced in Europe, where most of the precedents for American building types come from. These building traditions were brought to America through the different cultures that established colonies in the New World.

Thus, the cities laid out by the Spanish are significantly different from those laid out by the French, Dutch or English, not only in tradition, but also because of where each of these cultures settled in the New World.

In southern and Mediterranean climates, there is a lot of sun and heat. Having a building close to the ground is a plus, as the earth helps regulate temperature. Also, buildings usually don't exceed one or two floors to avoid heat rising up to higher floors. Traditional Spanish houses are long low affairs, with small courtyards giving a little light where necessary, but in general cool and dark.

Archetypal Spanish house.

In the northerly climates, it's important to let in light, so buildings tend to have tall windows, but they also need to deal with cold winters. Therefore, having a tall building is an advantage, as heat is retained through the stacking of floors. Keeping the lots small, narrow and nestled together helps retain heat.

These important factors explain why lots are the sizes they are. A city in the northern European tradition will have taller and narrower buildings. Lots would be relatively shallow, with a depth of only about 35' or so for the main block including requisite garden space. With these smaller lots, the block size could be relatively small as well.

Ideal block in Alexandria, Virginia: 350' x 450'

Looking at Alexandria, Virginia as an example, we see a more "southerly" northern house, having a main block of 35 feet or so with a small wing attached and a small garden behind. The lots in Alexandria are slightly deeper because of this side wing but still relatively shallow compared to the massive blocks you find in old Spanish colonial cities.

Archtypical Alexandria house.

San Buenaventura, (aka Ventura), California, where I lived for two years, has lots 400 feet by 400 feet, four times the size of Portland's blocks. Ventura was laid out according to the needs of a hot sunny climate. Like other buildings of the Spanish Colonial era, it has low, sprawling houses. This requires a lot more ground space, and so the lots need to be significantly deeper to allow room for a usable garden behind.

Ideal block in Ventura: 400' x 400'

Pre-industrial cities needed gardens to grow produce and even raise small livestock. Almost all food had to be raised locally, so having a garden was essential to city living. After the Industrial Revolution, with the advent of fast travel, food could be brought to market from distant lands, so the importance of a garden began to wane. Thus we can see why Portland, founded in the latter part of the 19th century, could afford to have relatively tiny blocks.

The industrial city becomes less and less subject to the necessities of the environment, and so most American cities west of the Appalachians have block sizes of more or less arbitrary sizes. Anchorage could afford to have a big block size just as much as it could have a smaller one.

Today, with the advent of cars and air conditioning, the size and shape of a lot has more to do with the needs of the car and its parking than any other concern. Lot sizes revolve less around depth, and more around width, being in multiples of car widths for the garage.

20 comments

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Erik Bootsma is a board member of the National Civic Art Society and of the Mid-Atlantic Chapter of the Institute of Classical Architecture and Art.

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Great job explaining the differences. I am curious how much of this was common knowledge 100-150 years ago when thousands of cities were incorporated throughout the west.

by Sid Burgess on Jun 2, 2010 3:21 pm • link • report

thnx. very interesting.

by Bianchi on Jun 2, 2010 3:24 pm • link • report

Wouldn't Jefferson's method of measuring/surveying have also affected the size of blocks. I forget the dimensions, but Jefferson came up with some standard that got used to apportion the land the US acquired as part of the Louisianna Purchase (and maybe for the Northwest territories? ... i.e., current day Ohio, IN, etc. which the US got as part of the Treaty of Paris ending the Revolutionary War.) I grew up in a town that pre-dated this measuring convention and hence had only a few true 'blocks' in it. I have to say, I don't like blocks. It makes a city dull. I think Washington's saving grace is the fact it has diagonals to soften the blocks. I remember meeting a Brit who really hated American cities because as a pedestrian he felt he constantly had to cross a street in order to get anywhere ... another downside to blocks vs. organically grown streets. But I guess, as L'Enfant knew (and Jefferson too) if you're going to get the most bang for your development buck, you go for blocks. Still I hate blocks ... It's just not a natural way of living.

by Lance on Jun 2, 2010 3:35 pm • link • report

Lance,

The Township and Range system certainly effected the location of town centers. Many small towns that I know of have their axis centered on the intersection of 4, 640 acre tracts (1 square mile).

Europe has blocks though your friend is very correct in identifying that our system is intersection heavy.
(http://bostonhistory.typepad.com/notes_on_the_urban_condit/2004/11/the_unweaving_o.html)

Their pattern appears to be more random but they are often-time planned to be precisely as such. I once heard it put that our lot and block system appears dull because our early planners were simply far less creative. :)

If you want to read more about "Emergent Urbanism" which is mostly the case for allowing for that planning to be more organic, I encourage you to follow Mathieu's site http://emergenturbanism.com

A post I recommend for initial discovery of the subject in depth is http://emergenturbanism.com/2009/10/05/defining-a-new-traditional-urbanism/

I have some documents (PDFs) that you also might find interesting on the subject that do well to explain the strength of the "chaotic" grid.

All the best.

by Sid Burgess on Jun 2, 2010 3:52 pm • link • report

In the upper right of this blogs page it says "TRAFFIC: street grids not freeways" - reflecting the "New Urbanist" orthodoxy: City blocks are good; suburban Feeder-and-arterials are bad. But I love urban pedestrian, transit and bike oriented life and I hate the city block.

The American city block manages to be simultaneously pedestrian unfriendly, cyclist unfriendly, transit unfriendly AND auto unfriendly. Since practically every street is a through street, there are intersections everywhere, and they get in everyone's way. In contrast, the feeder and arterial system gets one important thing right: There is a hierarchy of roads. Small roads lead to big ones, and big roads are only crossed by other big roads. In every European city I've lived, there is a similar hierarchy of urban thoroughfares: boulevards with major transit, wide sidewalks, multiple lanes of traffic, and (where I've lived) protected bike lanes; smaller roads with apartments, houses, calmed streets, parking and no need for bike lanes.

This is illustrated nicely in Berlin:

View Larger Map

Those yellow streets are major arterials. Essentially all traffic moves on the arterials - transit, bikes and cars. There are no curb cuts, and no street parking. There are few intersections and few left turns. The streetcars (in their own dedicated lanes) don't have to negotiate cross traffic and left turning cars. Cyclist don't have to contend with parking cars, cars pulling into the street, or stop signs and lights every block. And since the auto traffic isn't stopping at frequent intersections, cars maintain relatively high average speeds with low top speeds (speed limit: 30 mph). Same for buses. In short everybody wins.

This is the right model for urban thoroughfares.

We are fortunate in DC - we almost have a hierarchy of roads. But unfortunately it isn't taken seriously. If it were we would be limiting the number of through roads, and turning the major arterials into true boulevards (and not just the ones used by commuters) - but as this would limit auto capacity, I doubt this will ever happen.

by egk on Jun 2, 2010 6:35 pm • link • report

Interesting map when compared to a city like Indianapolis.

View Larger Map

by Sid Burgess on Jun 2, 2010 6:48 pm • link • report

Personally, I like the organization of blocks. Also I only have american cities and suburbs to compare since I've never been to Europe. Though I always took the concept of a street grid as a web of connections whether the blocks are square are not.

by Canaan on Jun 2, 2010 11:45 pm • link • report

Nice post, I love when people take the time to go beyond the surface to find the function underlying what most people just assume to be aesthetic preference. A good grid has a hierarcy of streets and blocks, much like was illustrated in the Berlin plan. Florence Italy started as a roman grid from which the medeival foot paths shoot out in a more organic flow. Whether a spagetti bowl (DT London) or a grid, connectivity and heirarchy is what allows for both an efficient flow of traffic and a pleasant pedestrian experience.

by Thayer-D on Jun 3, 2010 7:24 am • link • report

Most of the cities in the inland West and a lot of smaller towns in the East have the same size blocks because they were planned around the railroads. Anchorage, Tulsa, Bismarck, Missoula and Phoenix (shown in your graphic) were all laid out this way. In Anchorage the downtown area which was planned by the army is known as the "military grid" with numbered EW avenues and lettered NS streets. They made some local variations, though, like naming streets in the eastern addition alphabetically after Alaskan towns, and removing "J" street because the Scandinavian immigrants couldn't pronounce it.

by chris on Jun 3, 2010 9:55 am • link • report

I just returned from a meeting in the wonderful city of Portland, OR. The folks from the planning and transportation departments told all of us that Portland's mini-blocks came from the original speculators' hunch that corner lots commanded higher prices, so they wanted as many as possible. The side-effect of that capitalist quirk is a city that looks bigger on the map than it actually is. Portland's planners have made their fine-grained city fabric a model of livability

by Susan on Jun 3, 2010 10:11 am • link • report

Susan,

That idea was also mentioned here in this article.
http://www.planetizen.com/node/41290

by Sid Burgess on Jun 3, 2010 10:12 am • link • report

That's a great point Susan. My wife visited Portland and commented to me how she criss crossed the city when on the map it seemed to her it was going to take a lot longer. Now-a-days when I've worked with developers on New-urbanist projects, the offset to corner lots is the increased roads that have to be built. My understanding of most American grids is that they where efficient and practical, ideal for a mushrooming country like ours.

by Thayer-D on Jun 3, 2010 10:23 am • link • report

I like the concept of large front yard and small back one not the other way around.

If you look at older houses you will always see large front yards meant for play and front porches that can be used and are not just for show like the ones built today. It seems like the areas with the large front yards have a better sense of community and interacting with neighbors.

Wouldn't mind a grid that is completely straight where all streets go a certain way and don't just dead end to a park or something and start back up miles or blocks later.

by kk on Jun 3, 2010 1:36 pm • link • report

The article makes some good points, but completely overlooks the single most important determinant in North America: what the original developer or surveyor wanted to do. After all, San Diego blocks are the same size as Portland's, but the reason has nothing to do with Spanish traditions or climate. It's because the townsite developer wanted to be able to sell more corner lots. Very few American towns, especially outside New England, developed organically. Some speculator platted the land into blocks and lots based on what he thought would be most profitable or easiest to survey. A lot of railroad towns were platted by people sitting in Chicago or St. Paul offices, who never even saw the locus in quo.

by Dennis McClendon on Jun 3, 2010 9:25 pm • link • report

Though it was not considered when blocks were laid out, the size also controls the density of auto traffic. This is one reason the Portland is such a different pedestrian city than, say, Minneapolis. Twice as many streets and twice as much parking serves the same building area, so: more street surface but less traffic per street. The feeling is quite different.

by wally on Jun 4, 2010 12:02 pm • link • report

Great info!

by Stephanie Emmons on Jun 4, 2010 12:37 pm • link • report

Dennis,
The last two paragraphs make the distinction between pre-industrial revolution cities and post industrial. Most cities after the advent of railroad and quick transit made considerations about the size of lots less important so the size of the blocks becomes for the most part completely arbitrary. So when the railroad developer in the latter part of the 19th century lays out a grid, it can be of many different sizes. However when one looks at cites plotted before 1800, there is some amount of correspondence to the considerations I pointed out. Of course there are always exceptions, but I think a "for the most part" is good enough when dealing with an art such as urban planning.

by Boots on Jun 4, 2010 12:45 pm • link • report

The comments about the 200' square blocks in Portland, OR are interesting and mostly true, especially for the CBD area. But Portland has many residential neighborhoods where the "block mold" was broken. Breaking the traditional 200' block was a direct response to topography (west hills)and new trends in development planning that were emerging within East Portland during the late 19th and early 20th centuries (Ladd's Addition and Laurelhurst Park).

Many neighborhoods were also influenced by the construction of electric street-car lines. Most of these lines were abandoned over the years during the 1920's. It is rumored that some of the rails still exist under layers of pavement. The metro area is now spending considerable (well spent) treasure and energy to expand the newly re-created street-car lines. This effort will continue to make Portland, OR one of the most livable and enjoyable cities in the world. It would be interesting to see if the new street-car lines actually follow the path of the old abandoned lines - how does that saying go? "What is past is now prologue" - let's hope so!

by Richard Bryant, AIA on Jun 4, 2010 12:53 pm • link • report

Note to Lance who hates blocks: I love blocks. When I lived in the French Quarter in New Orleans, there were a dozen different ways I could zig-zag throught the Quarter when walking to work on Canal Street.

by Ron on Jun 4, 2010 1:42 pm • link • report

So your thesis seems to be that blocks in Naples or Seville are substantially larger than those in Bern or Cologne, due to climate. I have not noticed that to be the case.

In North America, are the blocks in St. Augustine or San Juan larger than those in QuÃ©bec City or Boston?

Incidentally, those interested in urban morphology might want to look at these books:

Reps, John W. The Making of Urban America: a History of City Planning in the United States. Princeton University Press, 1965.

Easterling, Keller. American Town Plans: A Comparative Time Line. Princeton Architectural Press, 1993.

by Dennis McClendon on Jun 6, 2010 9:42 pm • link • report