List of United States counties by population

List of United States counties by population
Title	List of United States counties by population
Country	United States
Source	United States Census Bureau
Year	2020
Footnote	Based on the 2020 United States Census

List of United States counties by population. This list ranks the counties and county-equivalents of the United States by population, based on data from the decennial United States Census. The 2020 United States Census serves as the primary source, with the United States Census Bureau providing official estimates for subsequent years. Understanding this ranking provides insight into demographic distribution, urbanization trends, and the shifting political and economic centers of gravity across the nation.

Overview

The United States comprises 3,143 counties and county-equivalents, including parishes in Louisiana, boroughs in Alaska, and independent cities in states like Virginia and Maryland. Population sizes vary dramatically, from counties with millions of residents to those with fewer than one hundred. The most populous jurisdictions are often centered around major metropolitan areas such as Los Angeles County and Cook County, which encompasses Chicago. This administrative structure is fundamental to local governance, influencing the allocation of resources for public schools, law enforcement, and judicial systems nationwide.

Top 10 most populous counties

The ten most populous counties are predominantly located in the nation's largest combined statistical areas. Leading the list is Los Angeles County, California, home to over 9.8 million people and containing the city of Los Angeles. It is followed by Cook County, Illinois, which includes Chicago, and Harris County, Texas, anchored by Houston. Maricopa County, Arizona, which contains Phoenix, has experienced significant growth, challenging the positions of longer-established populous counties like San Diego County, California and Orange County, California. Other counties in the top ten include Miami-Dade County, Florida, Dallas County, Texas, Kings County, New York, and Riverside County, California.

Top 10 least populous counties

The least populous counties are typically found in remote, rural regions with challenging geography or sparse economic activity. Many are located in the Great Plains states, such as Kalawao County on the island of Molokai, which is also the smallest county by land area. Other examples include Loving County, Texas, the least populous county in the contiguous United States, and several counties in Nebraska and South Dakota like Arthur County, Nebraska and McPherson County, South Dakota. These counties often have populations smaller than a typical urban city block and face unique challenges in providing services.

Population distribution by state

Population distribution among counties varies significantly by state. States with large geographic areas and concentrated urban centers, such as California and Texas, have a high degree of population inequality among their counties. In contrast, states with more uniformly distributed populations, like those in New England, often have smaller county-level disparities. Alaska and Delaware have few counties, while Texas leads the nation with 254. The political influence of counties is reflected in bodies like the United States Electoral College, where county-level results can determine statewide outcomes in swing states.

Historical population changes

Historical shifts in county populations mirror broader national trends, including westward expansion, post-war suburbanization, and the Sun Belt migration. Throughout the 20th century, counties in the Industrial Belt like those around Detroit and Cleveland saw growth stall or reverse, while counties in the Southwest and Southeast expanded rapidly. The housing market correction and the COVID-19 pandemic have also influenced recent migration patterns, with some populations moving from dense urban counties to suburban or exurban areas.

Data sources and methodology

The definitive source for county population data is the decennial United States Census, a constitutionally mandated enumeration. The United States Census Bureau also publishes annual Population Estimates and American Community Survey data, which provide intercensal updates and detailed demographic characteristics. Methodology involves direct counting, statistical sampling, and sophisticated demographic analysis. These figures are critical for practical applications, including the congressional apportionment, redistricting for the United States House of Representatives, and the distribution of federal funds through programs like the Medicaid program and the Federal-Aid Highway Act.

Category:Lists of counties of the United States Category:United States geography-related lists Category:Demographics of the United States