The 25 Largest US Counties by Area
The largest county in the United States is San Bernardino County, California, covering 20,057 square miles — larger than the states of 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.
Top 25 largest counties by area
Note: the data below shows state-level area, not individual county area. For county-level detail, use our interactive county map and hover any county for its full stats.
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.
Alaska's Yukon-Koyukuk Census Area alone is larger than Montana — yet it has fewer than 5,500 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: San Bernardino County, CA — 20,057 sq mi
- Smallest: Kalawao County, HI — 12 sq mi (a former leper colony on Molokai)
- Most populated: Los Angeles County, CA — ~9.8 million people
- Least populated: Loving County, TX — ~64 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 20,057 square miles take in most of the Mojave Desert, the eastern San Bernardino Mountains, and a strip of the Colorado River, because no smaller subdivision could have funded a sheriff and a courthouse across that terrain. The same logic explains Nye County, Nevada (18,182 sq mi) and Coconino County, Arizona (18,617 sq mi).
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 areasfor statistical purposes. The Yukon-Koyukuk Census Area alone covers about 145,500 square miles — larger than Montana, and home to roughly 5,400 people. The North Slope Borough is roughly the size of Minnesota. 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)
The smallest county-equivalents are a reminder that the category is a legal label more than a size class. Kalawao County, Hawaiicovers about 12 square miles on the Kalaupapa peninsula of Moloka'i and exists because the territory created a separate jurisdiction in 1905 to administer the Hansen's disease (leprosy) settlement there. New York County (Manhattan) is 22.7 square miles of dense urban grid, while Arlington County, Virginia — at 26 square miles — is the smallest self-governing county in the contiguous US, the result of a 1789 cession to form the District of Columbia and a later retrocession. All three are tiny for different reasons (public-health history, urban density, federal boundary-drawing), but they all count the same way in federal statistics.
What "land area" actually measures
Census Bureau county area figures come in two forms: land area and total area. Total area includes inland water — lakes, rivers, reservoirs — and in Alaska, also includes "coastal water" out to the state's seaward boundary. That distinction matters more than it sounds: by total area, the North Slope Borough is the largest county-equivalent in the country at roughly 245,000 square miles. By land area only, San Bernardino County leads the lower 48 with its 20,057 figure. Most published rankings (including this page) default to land area for consistency, but if you compare two sources and the numbers don't match, the most likely 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 3,143 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