The 25 Largest US Counties by Area

Counting Alaska, the largest county-equivalent in the United States is the Yukon-Koyukuk Census Area in Alaska — about 145,768 square miles of land, roughly seven times the size of the largest county outside Alaska. That title belongs to San Bernardino County, California, which covers 20,068 square miles — larger than New Jersey, Connecticut, Delaware, and Rhode Island combined.

Most of the largest US counties are in Alaska and the western states, where sparse population and vast public lands result in enormous administrative areas. The Bureau of Land Management manages much of the federal land in these counties.

Largest county-equivalents, including Alaska (top 25)

Alaska's boroughs and census areas dominate the top of the list, with San Bernardino County the largest entry from the lower 48.

Largest counties outside Alaska (top 25)

Excluding Alaska, the biggest counties are concentrated in the desert Southwest and Great Basin — California, Arizona, Nevada, Oregon and Wyoming.

Why are western counties so large?

When western territories were organized in the 19th century, the population was extremely sparse. Counties were drawn to cover entire regions that might contain only a few hundred residents. As population grew along the coasts and in river valleys, eastern counties were subdivided further — but western counties largely kept their original boundaries.

The Yukon-Koyukuk Census Area alone is larger than Montana (145,768 vs 145,550 square miles) — yet it is home to only about 5,028 residents. Alaska's scale extends beyond county boundaries: its 6,640-mile ocean coastline is longer than every other US state combined (see our US state coastlines ranking).

Large counties vs. small counties

To put county size in perspective, here's how the extremes compare:

• Largest overall: Yukon-Koyukuk Census Area, Alaska — 145,768 sq mi
• Largest outside Alaska: San Bernardino County, California — 20,068 sq mi
• Smallest county-equivalent: Falls Church city, Virginia — about 2.0 sq mi (an independent city)
• Smallest true county: Kalawao County, Hawaii — about 12 sq mi (a former leprosy settlement on Molokai)
• Most populated: Los Angeles County, California — 9,694,934 people
• Least populated: Loving County, Texas — 52 people

Why the West has giant counties

When western territories were organized between 1850 and 1900, Congress and territorial legislatures drew county lines across vast stretches of land that might hold only a few mining camps, a railroad town, and a federal fort. The economic logic was simple: each county had to be big enough to contain a working tax base, but the population was so sparse that "big" often meant tens of thousands of square miles. San Bernardino County, California is the clearest example — its 20,068 square miles take in most of the Mojave Desert, the eastern San Bernardino Mountains, and a strip of the Colorado River. The same logic explains Nye County, Nevada and Coconino County, Arizona, each above 18,000 square miles.

Alaska is a special case because the state didn't adopt the county system at all. The 1959 state constitution created boroughs for areas willing to incorporate and run their own local government, and left everything else as the Unorganized Borough, which the Census Bureau then split into census areas for statistical purposes. None of these are "counties" in the strict sense, but the Census Bureau counts them as county-equivalents in its official ANSI list.

The smallest counties (for contrast)

Whether the smallest county-equivalent is an independent city depends on what you include. Counting independent cities, the smallest is Falls Church city, Virginia, at about 2.0 square miles. The smallest that is a true county rather than an independent city is Kalawao County, Hawaii, about 12 square miles on the Kalaupapa peninsula of Moloka'i — a jurisdiction created in 1905 to administer the Hansen's disease (leprosy) settlement there. For urban contrast, New York County (Manhattan) is about 23 square miles of dense grid, and Arlington County, Virginia — about 26 square miles — is the smallest self-governing county in the contiguous US.

What "land area" actually measures

Census Bureau county area figures come in two forms: land area and total area. Total area adds inland water — lakes, rivers, reservoirs. Both tables above, and most published rankings, use land area for consistency; if two sources disagree on a county's size, the usual cause is one citing land area and the other citing total area. The Census Bureau's Gazetteer files publish both columns for every county.

Explore county data

• US County Map — choropleth of all 3,144 counties by population, income, age, and more
• County Map with Cities — explore any county with city markers and population data
• What County Am I In? — find your county by GPS or address
• Map Area Calculator — draw any shape and measure its area in sq mi, km, or acres
• Blank Map of the US — free downloadable map with county boundaries

Data source

County land area is from the US Census Bureau's 2026 Gazetteer files; population is the County Population Totals, Vintage 2025 (July 1, 2025 estimates). All figures are US Census Bureau data in the public domain.

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