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Census Urbanized Areas and MPO/TMA Designation

FAQ Topic 2: 2010 Urban Area Delineation

Where can I find a description of the urban area delineation process used by the Census Bureau?

For information on the process used by the Census Bureau to delineate 2010 urban areas, please reference this presentation, prepared by the Census Bureau Geography Division for the 2011 ESRI International User Conference (HTML or PowerPoint [12 MB]). Please direct any question to Census Bureau staff at (301) 763-3056 or

Did the Census use data from the American Community Survey (ACS) to define new UZAs, and therefore result in new MPOs?

No. The ACS is a replacement for the Census "Long Form" to report demographic characteristics of the population. It is not an official count of persons, and does not have block-level population counts that are needed for UZA definition. UZAs are defined in-part on population density at the Census block level.

Where can I find the list of 2010 UZAs and UCs?

The Census Bureau issued the list of 2010 urban areas in a Federal Register Notice on March 27, 2012. For the list of 2010 urban areas and additional related resources, visit the 2010 Census Urban and Rural Classification and Urban Area Criteria webpage. Please refer to the schedule for more important dates and milestones related to MPOs and TMAs.

Did the Census Bureau use 2000 urban areas as the starting point for creating the 2010 urban areas? Why did some territories that were previously part of one UZA in 2000 move to another UZA in 2010?

No, the 2010 urban areas were delineated from "scratch." The Census Bureau did not start with the 2000 urban area boundaries. Territory on the fringes of urban areas that are proximate or adjacent may have shifted from one area to another based on revised 2010 census block boundaries and population distribution/density patterns.

Why are there some unpopulated areas included in urban areas?

The meaning of "unpopulated area" is dependent on the geographic scale of reference-that is, does this refer to census blocks with zero population, or to portions of census blocks that are not populated?

Unpopulated areas have always been included in urban areas and, depending on location and context, can qualify for inclusion at various stages in the delineation of urban areas. These areas may encompass "downtown" business districts and other commercial/industrial areas that lack population but are surrounded by densely populated census blocks. Such areas typically have been included in an urbanized area via the enclave criteria. This ensures that the commercial and industrial cores that often form the basis for the existence of the urban area are included in the area.

Unpopulated portions of urban areas containing non-residential urban land uses can also include parks (e.g., Central Park in New York City or the National Mall in Washington, DC), schools and other institutional facilities that are part of the urban landscape. Other unpopulated areas may be included via the impervious surface criteria, particularly on the fringes of urban areas where large commercial and industrial areas may not meet enclave inclusion criteria. Hops and jumps that are used to join outlying densely settled areas with the main body of an urban area also may encompass unpopulated areas.

Census Block boundaries also play a role in that a census block may encompass parcels of land that contain population as well as parcels that lack population. If a census block qualifies for inclusion in an urban area based on its overall population density, then the unpopulated portions will also be included.

What was the impact of including the 2006 National Land Cover Database (NLCD) Impervious layer in the criteria?

The Census Bureau added the use of the impervious surface layer from the 2006 National Land Cover Database (NLCD) to better account for the presence of non-residential urban land uses, such as commercial and industrial locations, that historically were excluded from an urban area, either because the associated census blocks failed to meet minimum population density criteria or because they were not included via enclave and indentation criteria. "Impervious surface" criteria was added in part, to alleviate some of the needs to adjust urban boundaries to include industrial areas and suburban employment centers on the urban fringe.

If an Urban Cluster is within 2.5 miles from an UZA, should it be joined to the UZA?

There are multiple reasons why an urban cluster 2.5 miles from a UZA might not have been included. The area between the UZA and the UC might not have met the density criteria for a jump. Or, there might have been another jump along the same road connection, and since only one jump along a given road connection is allowed, the second jump would not qualify.

Please contact Census Bureau Urban Area Delineation Program staff at 301-763-3056 or for further information.

We have found some anomalies in our area. In one case, a subdivision was not included in a UZA. If it had been included, two UZAs would have been joined together. Why was this area excluded?

When delineating urban areas, the Census Bureau applied published criteria with geographic information contained within its geographic database (TIGER) and official 2010 Census population counts at the census block and census tracts levels of geography. All population density calculations rely upon official 2010 Census population counts and Census Bureau calculations of land area for census blocks and census tracts as defined for the 2010 Census. Please contact Census Bureau Urban Area Delineation Program staff at 301-763-3056 to discuss specific questions about your area.

Does it make sense that only some UZAs in my State had an increase in population density between 2000 and 2010? Wouldn't you expect all of them to increase in population density?

The addition of land for industrial areas, suburban employment centers, and smaller airports, may have diluted the density increases you were expecting to see.

Is it possible for UZA boundaries to overlap?

No. The Census Bureau assigns geographic areas to only a single UZA.

Updated: 3/18/2015
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