How Big Is The Average American County?
Most Americans are aware that there are 50 states in the US, but few realize there are more than 3,143 counties. Using a current Census Bureau geography of 3,144 counties and county equivalents, the average county-level area works out to roughly 1,120 square miles of land. Using the Census Bureau's Vintage 2025 national population estimate, the arithmetic average is about 108,700 residents.
However, size and population vary dramatically. Some counties cover less land than a major airport, while others are larger than several U.S. states. In population, some counties have fewer than 100 residents, while Los Angeles County counted about 10 million people in the 2020 Census. Below is a look at those extremes for counties only, not county equivalents such as Louisiana parishes or Alaska boroughs and census areas.
Landmass Extremes - Smallest Counties
Kalawao County, Hawaii
Kalawao County is the smallest county in the U.S. by land area, at just 11.99 square miles. It sits on the Kalaupapa Peninsula of Molokai, which became an isolation settlement for people with Hansen's disease in the 19th century. Unlike a conventional county, Kalawao is under the jurisdiction of the Hawaii Department of Health. It also has unusually strict access rules. Visitors need permits, and people under age 16 are not permitted to visit Kalaupapa. Kalawao County had 82 residents in the 2020 Census, and the Census Bureau's 2025 estimate was also 82.
Arlington County, Virginia
Arlington County is the smallest self-governing county in the U.S. It has about 26 square miles of land yet had an estimated 243,931 residents as of July 1, 2025. There are no incorporated cities or towns within Arlington, but the county contains the Pentagon and Arlington National Cemetery.
Landmass Extremes - Largest Counties
San Bernardino County, California
San Bernardino County is the largest true county in the U.S., excluding Alaska's much larger county equivalents. It has about 20,068 square miles of land, making it nearly 18 times the national county-level average. It is also larger in land area than nine states, including Maryland, Vermont, and New Hampshire. To put that another way, the combined land area of New Jersey, Connecticut, and Delaware is still smaller than San Bernardino County.
Coconino County, Arizona
Coconino County is the second-largest true county in the U.S., with about 18,616 square miles of land. That makes it more than 16 times the national county-level average and larger in land area than nine states. The county includes a large stretch of northern Arizona and part of Grand Canyon National Park. The park itself extends across both Coconino and Mohave counties.
Population Extremes - Least Populous Counties
Loving County, Texas
Loving County had just 64 residents in the 2020 Census, making it the least populous U.S. county at that census. The Census Bureau's Vintage 2025 estimate puts its population even lower, at 52. Its tiny residential population stands in sharp contrast with the amount of economic activity there. Census QuickFacts recorded 663 jobs at county employers in 2023, more than ten times its estimated 2025 population. Kalawao County, Hawaii, was the next-smallest true county by 2020 Census population, with 82 residents.
King County, Texas
King County is another of the country's least populous counties. It had 265 residents in the 2020 Census, while the Census Bureau's 2025 estimate placed it at 192. The county is also home to the historic 6666, or Four Sixes, Ranch. Its headquarters were established at Guthrie, the King County seat, in the early 20th century.
Population Extremes - Most Populous Counties
Los Angeles County, California
Los Angeles County counted about 10 million residents in the 2020 Census, more people than lived in 40 individual U.S. states at the time. Its population has since declined somewhat, with the Census Bureau estimating about 9.7 million residents as of July 1, 2025. Even at that level, its population is roughly 89 times the current county-level national average.
Cook County, Illinois
Cook County had about 5.3 million residents in the 2020 Census and an estimated 5.2 million in 2025. The 2020 count represented about 41 percent of Illinois' population. Another surprising feature is how much protected land exists in such a heavily populated county. The Forest Preserves of Cook County surpassed 70,000 acres in 2024, accounting for more than 11 percent of the county.
The Big Picture
The county classification is difficult to reduce to a formula. It appears to be more a case of people settling in a spot and then deciding where the line should be. There is also a huge population disconnect as roughly half of the US population is found in just under 5% of the counties. Even more interesting is that our population is always moving, with some counties growing and others losing residents.
Kalawao County covers less than 12 square miles, while San Bernardino County is more than 1,600 times larger. Loving County counted only 64 residents in the 2020 Census, while Los Angeles County had roughly 10 million. These extremes, as is true for many facets of America, make it difficult to pin down what an "average" county even is.
