List of the most populous counties in the United States

This is a list of the 100 most populous of the 3,144 counties in the United States based on the national decennial US census conducted on April 1, 2020, and vintage Census population estimates for July 1, 2023.

[1] Many of the counties on the list include major cities or metropolitan areas in all parts of the United States.

Many of the most populous counties listed are in Southern California, Texas, and New York, and roughly correspond to several of the most populous cities or municipalities in the United States.

Counties in the Western United States are typically larger by area and therefore often have higher absolute populations even with comparable population densities.

This list includes the most populous US counties sorted according to both the 2020 official enumeration and 2023 vintage population estimates by the United States Census Bureau (USCB).

A map of the counties and county equivalents of the United States. The 100 most populous counties are highlighted, with counties having more than one million residents in orange and counties having fewer than one million residents in green, based on the results of the April 1, 2020 United States census .