In 45 of the 50 states of the United States, the county is used for the level of local government immediately below the state itself. Louisiana uses parishes, and Alaska uses boroughs. In Connecticut, Massachusetts, and Rhode Island, some or all counties within states have no governments of their own; the counties continue to exist as legal entities, however, and are used by states for some administrative functions and by the United States Census bureau for statistical analysis. There are 3,242 counties and county equivalent administrative units in total, including the District of Columbia and 100 county-equivalents in the U.S. territories.
There are 41 independent cities in the United States. In Virginia, any municipality that is incorporated as a city legally becomes independent of any county. Where indicated, the statistics below do not include Virginia's 38 independent cities.
In Alaska, most of the land area of the state has no county-level government. Those parts of the state are divided by the United States Census Bureau into census areas, which are not the same as boroughs. The state's largest statistical division by area is the Yukon–Koyukuk Census Area, which is larger than any of the state's boroughs. Although Anchorage is called a municipality, it is considered a consolidated city and borough.
New York City is a sui generis jurisdiction, in which the city government consists of 5 boroughs each coterminous with a county of the State of New York
Alaska has no counties. The following areas in Alaska are counted as county-equivalents: the 19 organized boroughs and, in its Unorganized Borough, 11 designated census areas
8 of the 14 counties in Massachusetts were disincorporated in the 1990s and early 2000s; local government in these areas consists of cities and towns. One of the remaining 6 counties is a consolidated town-county
The U.S. Minor Outlying Islands does not have counties. The 9 islands in the U.S. Minor Outlying Islands are counted as county-equivalents by the U.S. Census Bureau
The 3 districts and 2 unorganized atolls of American Samoa are counted as county-equivalents by the U.S. Census Bureau. American Samoa locally has 14 “counties”, but these “counties” are not counted as counties by the U.S. Census Bureau (they are treated as “minor civil divisions”)[2]
The Northern Mariana Islands has no counties. The 4 municipalities of the Northern Mariana Islands are counted as county-equivalents by the U.S. Census Bureau
The District of Columbia has no counties; the District of Columbia is considered both a state-equivalent and a county equivalent for statistical purposes[4]
Guam has no counties; Guam is considered both a state-equivalent and a county-equivalent for statistical purposes by the U.S. Census Bureau (similar to the District of Columbia)[2]
Total (50 states and District of Columbia): 3,143 (3,007 counties and 136 county equivalents)
Total (50 states, District of Columbia and territories): 3,243 (3,007 counties and 236 county equivalents)
Average number of counties per state (not including D.C. and the territories): 62.84[note 1]
Average number of counties per state (including D.C. and the territories): 56.8947368421[note 2]
The following is a list of the least populous counties and county-equivalents in all U.S. territory. Note that the only entity on this list with a permanent human population is Swains Island, American Samoa. The first 8 counties (county-equivalents) are uninhabited, while the 10th on the list (Palmyra Atoll) has a small non-permanent human population whose maximum capacity is 20 people.[6]
Smallest population counties in all U.S. territory (2020 Census)[7]
The largest counties and county-equivalents are organized boroughs and the census areas of Alaska with the top two being Yukon–Koyukuk Census Area (145,504.79 sq mi or 376,855.7 km2) and North Slope Borough (88,695.41 sq mi or 229,720.1 km2). The smallest counties and county equivalents (in the 50 states) are the independent cities of Virginia with the extreme being Falls Church at 2.05 sq mi (5.3 km2; 1,310 acres).[8] If the U.S. territories are included, the smallest county-equivalent is Kingman Reef, with a land area of 0.012 square miles (3.1 ha; 7.7 acres).[9]
The following two tables exclude county-equivalents:
Largest counties by land area nationwide (excluding county-equivalents)[8]
The following is a list of counties and county-equivalents showing the average size of each state/territory's counties, the smallest county (or equivalent) in each state/territory, and the largest county (or equivalent) in each state/territory. States/territories on the list are arranged by the average land area of their counties. Though not on the list, the North Slope Borough is the largest independently incorporated county equivalent. The Unorganized Borough is substantially larger, but is an extension of the State of Alaska government and not independently incorporated.[A]
Also note that the smallest land area with county-level governance in the U.S. is Falls Church, Virginia, but it is an independent city and not a county or part of one. Kingman Reef is the smallest county-equivalent in all U.S. territory (though it has no government). Kalawao County, Hawaii is the smallest true county by land area.
Smallest, largest and average land areas for counties and county-equivalents by state and territory[10]
Data presented below is based on U.S. Census department data from 2010.[10] Calculations are made by dividing the population by the land area. All county equivalents are included. This list includes the 50 most densely-populated counties and county-equivalents in the 50 states and District of Columbia, plus the 9 highest-density municipalities (county-equivalents) of Puerto Rico. Puerto Rico is the only U.S. territory with population densities (of county-equivalents) high enough to be on this list. Note that many of these high-density counties are coterminous with large cities (for example San Francisco and Philadelphia) or are independent cities in Virginia (as well as Baltimore and St. Louis) which are considered county-equivalents.
This list was generated by dividing the population by the land area. All county equivalents are included. The list is dominated by just a few states: Alaska, Montana, and Texas together comprise about two-thirds of the entries. The Unorganized Borough is not included here as a unit, but its census areas (non-governmental entities) are. If the census areas were removed from the list, the Unorganized Borough would rank fourteenth with a density of 0.38 per square mile (0.15/km2).
The 8 uninhabited county-equivalents in the U.S. territories are listed at the top of the table — these are technically the least-densely populated counties/county-equivalents in the United States, but since they have no people, they are listed unranked.
Data presented below is based on U.S. Census Bureau data from 2010.[10] Calculations are made by dividing the population by the land area. All county equivalents are included.
Excluding the census areas of Alaska, Lake and Peninsula Borough is the least densely populated county equivalent with 0.069/sq mi (0.027/km2).
The District of Columbia and Guam each only have one county-equivalent, so their most/least densely-populated county is the same.
^A: The Unorganized Borough, Alaska, formed by the Borough Act of 1961, is a legal entity, run by the Alaska state government as an extension of State government,[11] it and the independently incorporated Unified, Home Rule, First Class and Second Class boroughs roughly correspond to parishes in Louisiana and to counties in the other 48 states.[12]
^Number produced by diving 3,142 by 50 — Note it is 3,142 and not 3,143 (because the District of Columbia is not counted)
^Number produced by dividing 3,243 by 57 (the number 57 represents the 50 states, the District of Columbia, the 5 inhabited territories, and the U.S. Minor Outlying Islands as one entity
^If including water area, the average county size of counties and county-equivalents in all U.S. territory is 1,172.38 square miles
^The least-densely populated inhabited county-equivalent in American Samoa is Swains Island, which has 18.1 people per square mile.
^The least-densely populated inhabited county-equivalent in the Northern Mariana Islands is Tinian Municipality, which has 75.0 people per square mile.
^"Chapter 4: States, Counties, and Statistically Equivalent Entities". Geographic Areas Reference Manual(PDF). U.S. Department of Commerce. November 1994. p. 4-2.