The U.S. Census Bureau announced today that the U.S. population is more urbanized than ever before. In 2000, 79.0% of the population lived in an Urban Area, as defined by the Census Bureau, and in 2010 that number grew to 80.7% of all Americans. While this finding might suggest that Americans are moving into the kinds of urban places featured on this blog – walkable neighborhoods with a diversity of uses in close proximity – the full story is much more nuanced. “Urban” can mean many things.
While the urbanized population grew between 2000 and 2010, the area of land considered urbanized grew by even more. This requires some explanation of the terms. The Census determines two types of Urban Areas, using a complex set of mapping criteria based on neighborhood-scale population density, impervious surfaces, and other factors. There are “Urbanized Areas” of 50,000 people or more, and “Urban Clusters” of 2,500 people or more. These are important geographies because, unlike metropolitan areas or incorporated cities, they are based on the results of the census. They are not arbitrary lines on the map but a description of the facts on the ground.
Before looking at some results, I’d like to note that the minimum density threshold to qualify an area as urban is not all that high. An area must have core Census Tracts with at least 1,000 people per square mile, and the urbanized area can spread out indefinitely as long as there are contiguous areas with 500 people per square mile. It can even “jump” and “hop” over sparsely populated land to continue along a corridor. As a point of reference, a neighborhood of single-family houses on two acres lots would qualify as “urban” under this definition, even considering roadways and other leftover spaces.