OMB Metropolitan and Micropolitan Area Delineations
The official list of which counties belong to which metropolitan or micropolitan statistical area.
The Office of Management and Budget defines a metropolitan or micropolitan statistical area as "a core area containing a substantial population nucleus, together with adjacent communities having a high degree of economic and social integration." A metropolitan area contains an urban area of at least 50,000 people; a micropolitan area contains one of 10,000 to 49,999. OMB has held responsibility for these delineations since 1949, and the Census Bureau distributes the resulting county lists.
Coverage#
We use the July 2023 delineation file, which reflects the 2020 standards announced in OMB Bulletin 23-01. It names 935 statistical areas and assigns 1,915 county-equivalents to them. We use the fifty states and the District of Columbia.
Delineations are revised on no fixed schedule. OMB updates the standards roughly once a decade and issues intercensal revisions between them, so a metro area's county membership is not fixed over time.
How we use it#
This file is the authority for which counties make up a metropolitan or micropolitan area. It lets county-level information be assembled into metro-level figures, and lets metro-level figures published by other agencies be matched to the counties they describe. It is a reference geography and produces no metric of its own.
Considerations#
Because area boundaries change, a long series compared across a delineation revision may reflect a change in which counties are counted rather than a change in the places themselves. Areas that gain or lose counties are most affected.
Citation#
U.S. Office of Management and Budget, Metropolitan and Micropolitan Statistical Area Delineations, July 2023 (OMB Bulletin 23-01), distributed by the U.S. Census Bureau.
Per Census Bureau guidance, the Bureau is cited as the source of the original data only.
References#
- 1US Census Bureau / OMBhttps://www.census.gov/programs-surveys/metro-micro/about/delineation-files.html
- 2OMB Bulletin 23-01https://www.whitehouse.gov/wp-content/uploads/2023/07/OMB-Bulletin-23-01.pdf
- 3Census Bureau guidancehttps://www.census.gov/about/policies/citation.html