Urban Influence Codes

The 2024 Urban Influence Codes are a nine-category county classification based initially on the Office of Management and Budget’s 2023 three classifications—metropolitan, micropolitan, and noncore counties:

• Metropolitan (metro) counties are divided into two categories based on the population size of the metro area (greater than or less than 1 million people).
• Micropolitan (micro) counties are divided into three categories based on their adjacency to metro areas of different sizes (adjacent to a large metro, adjacent to a small metro, and nonadjacent).
• Noncore nonmetropolitan (nonmetro) counties are divided into four categories based on their adjacency to large and small metro areas and the population size of their largest city or town (greater than or less than 5,000 residents).

Each county and census-designated county-equivalent in the United States is assigned a code, including those in outlying territories.

The Urban Influence Codes (UIC) were first created in 1997 based on population data from the 1990 decennial census and the 1993 delineation of metropolitan areas by the Office of Management and Budget (OMB). USDA, Economic Research Service (ERS) updated the Urban Influence Codes after each subsequent decennial census, including this latest version based on 2020 population data and OMB’s 2023 delineation of metropolitan and micropolitan areas.

The 2024 Urban Influence Codes use similar criteria and methods as previous delineations. However, they have been consolidated from 12 to 9 categories and rearranged to make the codes more intuitive and to better emphasize the role of urban influence as measured by adjacency.

See the Documentation for details and a map of the codes.