Which is the largest US county, and which is the smallest?
Four different right answers, depending on whether you mean area or population and whether Alaska counts.
Four answers are defensible, and the one you want depends on two things that have to be settled first: which measure you mean, and whether the place has to be legally a county.
| Question | Answer | Figure |
|---|---|---|
| Largest by land area | Yukon-Koyukuk Census Area, Alaska | 145,767.49 sq mi |
| Largest that is legally a county | San Bernardino County, California | 20,068.42 sq mi |
| Smallest by land area | Falls Church city, Virginia | 2.05 sq mi |
| Smallest that is legally a county | Kalawao County, Hawaii | 11.99 sq mi |
| Largest by population | Los Angeles County, California | 9,694,934 |
| Smallest by population | Loving County, Texas | 52 |
The biggest one is not a county
Yukon-Koyukuk Census Area in interior Alaska covers 145,767.49 square miles of land, which is larger than most states. It is the largest county-equivalent in the country by a margin nothing else approaches.
It is also not a county, and it is not a government. A census area is a Census Bureau subdivision of Alaska’s Unorganized Borough, and the eleven of them exist so that the parts of the state with no organised local government still have a statistical unit to report data against. Yukon-Koyukuk has no government and no county seat.
Alaska has 30 county-equivalents: 13 boroughs, 4 cities and boroughs (Juneau, Sitka, Wrangell and Yakutat), 2 municipalities (Anchorage and Skagway), and 11 census areas. The census areas are Aleutians West, Bethel, Chugach, Copper River, Dillingham, Hoonah-Angoon, Kusilvak, Nome, Prince of Wales-Hyder, Southeast Fairbanks and Yukon-Koyukuk. For how that system works, see why Alaska has boroughs.
The Alaska entities dominate the top of the list:
| Rank | Entity | State | Land area (sq mi) |
|---|---|---|---|
| 1 | Yukon-Koyukuk Census Area | Alaska | 145,767.49 |
| 2 | North Slope Borough | Alaska | 88,792.78 |
| 3 | Bethel Census Area | Alaska | 40,654.88 |
| 4 | Northwest Arctic Borough | Alaska | 35,671.70 |
| 5 | Southeast Fairbanks Census Area | Alaska | 24,839.23 |
| 6 | Matanuska-Susitna Borough | Alaska | 24,707.12 |
North Slope Borough, second at 88,792.78 square miles, is an organised borough rather than a statistical area, so it has its own government. If the requirement is only that the entity governs itself, that is your answer; if it is the word county, you have to leave Alaska.
The largest place actually called a county
San Bernardino County, California, at 20,068.42 square miles, is the largest county outside Alaska and the largest entity anywhere carrying the legal designation. Its territory runs from the eastern edge of the Los Angeles basin out to the Nevada and Arizona state lines.
The next few are the same desert and plateau geography:
| Entity | State | Land area (sq mi) |
|---|---|---|
| San Bernardino County | California | 20,068.42 |
| Coconino County | Arizona | 18,616.37 |
| Nye County | Nevada | 18,181.91 |
| Elko County | Nevada | 17,173.30 |
The full ordering, with and without Alaska, is on the largest counties by area ranking.
The smallest one is not a county either
The smallest county-equivalent by land area is Falls Church city, Virginia, at 2.05 square miles, and the next five entries are independent cities too:
| Entity | State | Land area (sq mi) |
|---|---|---|
| Falls Church city | Virginia | 2.05 |
| Lexington city | Virginia | 2.50 |
| Manassas Park city | Virginia | 3.03 |
| Covington city | Virginia | 5.47 |
| Fairfax city | Virginia | 6.24 |
| Buena Vista city | Virginia | 6.44 |
Virginia has 133 county-equivalents: 95 counties and 38 independent cities. An independent city sits outside any county, provides both city and county services, and is its own county-equivalent for federal statistics. That is why they appear in county tables at all, and why they crowd out every county at the small end. Fairfax, Franklin, Richmond and Roanoke each exist as both a county and a city, and the Census Bureau writes the city suffix in lower case, so “Fairfax city” and Fairfax County are separate records. The mechanics are set out in what an independent city is.
Filter to entities legally called counties and the answer becomes Kalawao County, Hawaii, at 11.99 square miles. Kalawao is unusual in a second way: it has no county government in the ordinary sense, and its mayor is by law the Director of the Hawaii Department of Health. Its population of 82 also makes it the second smallest county-equivalent. The rest of the small end is at smallest counties by area.
By population, the answers are cleaner
Population is the one measure where entity class does not complicate things. Los Angeles County, California, holds 9,694,934 people, more than most states, and the top of the list is all ordinary county governments.
| Entity | State | Population |
|---|---|---|
| Los Angeles County | California | 9,694,934 |
| Cook County | Illinois | 5,194,625 |
| Harris County | Texas | 5,045,026 |
| Maricopa County | Arizona | 4,689,558 |
| San Diego County | California | 3,282,248 |
At the other end, Loving County, Texas, has 52 residents.
| Entity | State | Population |
|---|---|---|
| Loving County | Texas | 52 |
| Kalawao County | Hawaii | 82 |
| King County | Texas | 192 |
| Kenedy County | Texas | 319 |
| McPherson County | Nebraska | 369 |
| Arthur County | Nebraska | 396 |
These are Population Estimates Program figures, Vintage 2025, an annual estimate rather than a headcount. See most populous counties and least populous counties for the full tables.
That matters if you want anything else about the small counties. The American Community Survey publishes 1-year estimates only for areas of 65,000 or more, which is 845 of the 3,144 county-equivalents; the other 2,299 have 5-year estimates only, so a figure for Loving or Kalawao is pooled over five years of sample.
What the ranking is counting
These rankings run over the 3,144 county-equivalents in the 50 states and DC; add Puerto Rico’s 78 municipios and the island areas and the count is 3,235.
Only 2,999 of those entities are called County. The rest are 64 Louisiana parishes, 40 independent cities, 13 boroughs, 11 census areas, 9 Connecticut planning regions, 4 cities and boroughs, 2 municipalities, and 2 with no type word at all. Governance varies as much as size: 35 entities have no county government, 21 have no county seat, and 54 are their own seat.
Land area is not total area
The figures here are land area, water excluded, and that choice changes the ordering. Total area counts the water inside a boundary, so a place with a large bay or lake sits higher on a total-area list than on a land-area one. A table that does not say which measure it uses cannot be reconciled with one that does.
Boundary files carry the same trap: raw TIGER/Line county polygons run out into territorial water, so a TIGER map of Virginia fills the whole Chesapeake Bay and fuses the Eastern Shore to the mainland. The maps here use the cartographic boundary files at 1:500,000, pre-clipped to the shoreline.
Sources also disagree because they rank different classes of entity without saying so: a list that quietly drops Alaska gives San Bernardino, one built straight from a Census file gives Yukon-Koyukuk.
State the measure and the class
The honest answer names the measure and the entity class before it names the place. Largest by land area: Yukon-Koyukuk, or San Bernardino if it has to be legally a county. Smallest by land area: Falls Church city, or Kalawao under the same filter. Largest and smallest by population: Los Angeles and Loving.
Anyone who gives you one name without saying which two filters produced it has skipped the part of the question doing the work.