We are used to dealing with jurisdictional boundaries when assessing and comparing cities. These are often either municipal areas or metropolitan statistical areas (which are based on entire counties). But these can have little relevance to the amount of area in a given city-region that is actually urban in nature. This makes apples to apples across regions difficult.
Once a decade though the Census Bureau gives us a more detailed look. They release definitions of so-called “urbanized areas” that attempt to look at just the amount of land that is actually urban in form. In theory this would allow for better apples to apples comparisons between regions. Unfortunately, most data is not sliced this way, so we only get this glimpse. Here’s the map of the new 2010 urbanized area definitions:
Wendell Cox has a breakdown of the largest urbanized areas that includes density. He also published a historical review that tracks urbanized area population and density since 1950 for the largest city regions. For more thoughts on urbanized areas, see Nate Berg’s take over at Atlantic Cities.
I don’t want to try to offer a complete analysis of this right now, but one thing that really jumped out at me was the very low densities of some southern boomtowns like Atlanta (1,707/sq. mi) and Charlotte (1,685/sq. mi.). Contrast with even Houston (2,979/sq. mi.) and Dallas (2,879/sq. mi) and see the difference. Atlanta is already showing serious signs of weakness vs. the Texas mega-metros and I wonder if this is part of the reason why. It also makes me wonder if Charlotte might someday suffer in a similar manner if its growth ever flames out.