The big, dense cities of America

I was having a discussion on Twitter—as I am wont to do—about the densities of cities in the United States. The discussion turned to when various cities had reached peak density and I realized I had compiled such a list in a Google Doc several years back. When I’d created the document I’d set a lower limit to the size of city included (about 60,000) and the peak density (10,000 per square mile), but was more interested in the larger cities. Right now (well, as of the 2010 census), there are six cities with at population of at least 500,000 and a density of at least 10,000, in order:

New York (8.2m, 27k/sqmi)
Chicago (2.7m, 12k/sqmi)
Philadelphia (1.5m, 11k/sqmi)
San Francisco (805k, 17k/sqmi)
Washington DC (618k, 10k/sqmi)
Boston (618k, 13k/sqmi)

None of these cities will likely fall below either threshold any time soon (although for a few decades, DC was below 10,000 per square mile). Some cities may join: Long Beach is about 35,000 away from reaching this density, Seattle would need to add 150,000 and Los Angeles 700,000. Miami, which has a density of 11,000, would have to add 60,000 residents to reach 500,000. In addition, it should be noted that each of New York’s boroughs (except Staten Island) would qualify for the list as well.

But the list hasn’t been static, and in 1950, there were an additional six cities meeting this threshold, cities which are far smaller and less dense now than then. They are:

Detroit (1.8m/13k, now 713k/5.1k)
Baltimore (950k/12k, now 621k/7.7k)
Cleveland (915k/12k, now 397k, 5.1k)
St Louis (857k/14k, now 319k/5.2k)
Pittsburgh (677k, 12k, now 306k, 5.5k)
Buffalo (580k/14.2k, now 261k, 6.4k)

This almost perfectly defines the Rust Belt, and these cities have emptied out in the past 60 years. Chicago, Philadelphia, DC and Boston all started with similar trajectories in the 1960s and 1970s, but have arrested their falls and remain as large, dense cities. With the exception of Baltimore and Detroit, each of these Rust Belt cities is now below both 500,000 and 10,000, and Detroit has lost two-thirds of its population and is only above 500,000 because it’s baseline—the fourth largest city in the country in 1950 (behind NYC, Chicago and Philly)—was so high. 1950 was the peak of density in the United States, and it will be a long time until we have as many large, dense cities as we had then.

While these cities certainly had less-diversified economies than the cities which have stayed on the list, they haven’t done themselves any favors. New York, Chicago, Philadelphia and Boston all have extensive mass transit systems; DC and San Francisco have build them (other than Detroit, the dense Rust Belt cities all have some sort of mass transit, but nowhere near the extent of the six large cities; the Big Six today are also the cities with the highest transit mode share in the country). Most also limited the spread of highways in their urban areas, something which didn’t occur in the Rust Belt cities. Policies which encouraged residents to leave the city worked too well, and these cities are now half-abandoned, or more, despite being as dense as their peers 60 years ago.

Not all cities peaked in 1950. If we expand our criteria to cities which peaked at at least 60,000 people (keeping the 10,000 density requirement) and include New York boroughs, we’ve seen peak population densities stretching back a century.

The first was in 1910 when Manhattan reached its all-time peak of 2.3 million residents, a density of 101,548 per square mile. The list of cities (at least those with at least one million residents) which have ever achieved such density is short: Manila. And it’s only about half the size of New York. Paris, at 55,000 per square mile, is the densest western city today. In 1910, New York had as many people in half the space. Once subways opened allowing easy access off the island it was a safety valve, allowing people to move out of jammed tenements to the relatively spread-out outer boroughs.

One city, Lawrence, Mass., peaked in 1920 (the Merrimac valley could be called the linen belt 100 years ago as its textile mills moved south). Two peaked in 1930: Somerville, Mass. and Jersey City, N.J. In 1940, Providence, R.I. peaked (and is the first city on this list to have fallen below 10,000, although barely).

1950 was the peak; in addition to the cities above, Brooklyn, Philadelphia, DC and Boston peaked, as well as several smaller cities. Cities which peaked in 1950 have, in general, fared far worse than those which peaked before or after. The only cities which have seen their populations decline by more than half peaked in 1950, in fact, the average decline for 1950-peakers—65% (although this doesn’t include cities like San Francisco which peaked in 1950 and have since surpassed that)—is lower than any other city on the list.

The Bronx peaked in 1980 (Queens is larger today than it has ever been), and no city, large or small, peaked in the 1990s. Several small jurisdictions peaked in 2000, and as of 2010, New York City as a whole, Queens, San Francisco and Miami and several other small cities are at their peak.

There are, however, two other “cities” which could be included on the list, that is, if you were to agglomerate small, dense suburbs of large cities. (Combined with Hialea, Miami Beach and some others, Miami would also make the list.) One is (not surprisingly) in New Jersey, where just the stretch from Bayonne to Fort Lee boasts nearly 700,000 residents at a density of 17,000 per square mile—similar to San Francisco. The other is north of Boston. Somerville, Chelsea, Cambridge, Malden and Everett all fall above 10,000, but only have 308,000 people (albeit in just 22 square miles). Add in Winthrop, Watertown, Revere, Arlington and Medford and you have an arc north of the city with 505,025 people living in 48.8 square miles—a population density of 10,340. Boston has by far the largest percentage of residents in 10,000+ jurisdictions outside the major city (37%, SF and NY are 26 and 21, the others are under 10) and all but Lawrence are contiguous. So if the cities and towns north of Boston combined to form, say, North Boston, or Chamedwathronfordville, it would be a pretty big place.

Why the 2010 census does not paint a full picture

In a recent post, Andrew Sullivan linked an article by Joel Kotkin arguing that the trends shown by the 2010 census show a continuing flight both from cities to suburbs and from denser cities to less dense ones. This page has never been a fan of Kotkin, who is continually trying to reprove his thesis from 2005 that the suburbs were the way of the future and that the cities of the future were “Orlando, Fla., San Bernardino-Riverside, Calif., Phoenix and Las Vegas.” (Seriously, this 2005 piece gets just about everything wrong.)

I am not going to waste time arguing several of the points Kotkin raises (for instance, he extols falling condo prices without mentioning that suburban house prices in many markets have plummeted just as much) or go in to the politics of subsidized home ownership (Sullivan uses another blogger to point out that high urban housing prices stem from high demand and policies which restrict growth in supply, further subsidizing suburban housing). Instead, I am going to look at recent, post-housing bubble data that shows that Mr. Kotkin’s thesis may be based mostly on the first half of the decade, not recent years. (He goes on to compare the 2009 American Community Survey and the 2010 Census, which are different data sets—so he’s comparing apples to oranges.)

To do so, I am going to use the census data beautifully displayed by Forbes (and commented on by several, including the Kotkin). I’ll concur with one of the other commentaries (all are worth reading, especially interesting is one point out the income difference between in- and out-migration) that there are large swings between 2005 and 2009, but point out that they are not only between certain cities but within them as well.
For each, I’ll show the migration chart from 2005 to 2009, and then the local migration maps from 2005 and 2009. And, yes, it would be great to have data on a more granular level (i.e., by zip code) or more aggregated level (by metropolitan area) but these doen’t exist, as far as I can tell.
1. Suffolk County, Mass. (Boston)

In the second half of the decade, out-migration from Suffolk Country went from well outpacing in-migration to falling behind it, and it fell while in-migration slowly rose. Locally, adjacent counties in eastern Massachusetts were recipients from Suffolk County each year, but further-flung counties, including sprawl-heavy Worcester County and those in Southern New Hampshire, flipped from receiving many migrants to giving them back.

Further afield, in 2005 Boston lost migrants to most every sprawling metropolis, including Dallas, Las Vegas, Atlanta, Charlotte, Jacksonville, Orlando and Miami. It gained population from all these centers in 2009. Middlesex County, including the very dense cities of Cambridge and Somerville (but large exurban areas as well adjacent to New Hampshire) shows similar, if less pronounced, trends.

2. Philadelphia County, Penna.

Philadelphia’s migration trends are not as pronounced as Boston’s—there is no switch from net out-migration to net in-migration—but it mirrors those of its northeastern neighbor. In the region, we can note a pronounced shift away from migration to far-flung suburbs, especially the second ring in Pennsylvania and New Jersey. There are similar shifts to the nearby suburbs in both years (and a similar draw from North Jersey) but the out-migration to the exurbs disappears. On the national front, there were fewer major shifts (like in Boston) but still several trends away from less-dense areas.

3. Washington, D.C.

The demographic trends for Washington show similar patterns, especially on the national scale. It’s out and in migration flipped, like in Boston, although the changes were less pronounced, as it never had the same mid-decade baseline losses as Boston. Locally, there was less movement towards some outer suburbs, although this can be confounded by the presence of Baltimore to the north, which doesn’t really qualify as a D.C. suburb. Still, there was less movement to counties far off in Northern Virginia in 2009 than 2005. Nationally, DC lost residents to Charlotte, Atlanta, Phoenix, Las Vegas and Los Angeles. By 2009, it was gaining residents from all of these.

While I wish I could go on this thread forever, I can’t, because the data (here, at least) is at the wrong scale. New York City is broken in to counties, and it’s so big that each county has different trends since there is so much migration within the city, as well as in to the city from the rest of the country. San Francisco doesn’t show such trends within the metropolitan area because the population is so spread across counties, and except for SF itself, most of the counties have significant urban and rural populations. But, further afield, San Francisco saw dramatic changes: in 2005 it lost significantly to LA, Las Vegas and Phoenix, in 2009 it gained population from these three cities. And in Atlanta and Chicago (Fulton and Cook counties), there weren’t major changes in national out-migration, but dramatic reductions in moves to the outer suburbs.

In any case, go and explore the Forbes map. It’s a lot of fun, both from a geography-nerd level and an exercise in proving Joel Kotkin wrong.