Colusa County area

Population and density of Colusa County

The Census Bureau estimates that 21,836 people lived in Colusa County on July 1, 2025. That ranks #1,782 of 3,222 county equivalents nationally and #50 of 58 in California. Since the April 1, 2020 estimates base of 21,835, the population has grown by 1 (+0%), compared with −0.5% for California as a whole.

With 1,150.6 square miles of land, that is 19 people per square mile (7.3 per km²), placing Colusa County #2,358 nationally for density and #48 in California. The median county equivalent has 47 people per square mile; the California median is 112. Put another way, there are about 34 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Colusa County

2 incorporated places lie at least partly in Colusa County. Together they are home to 12,048 people (55.2%); the other 9,788 (44.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Colusa city, with 6,519 residents in the county. By land, Williams city is the largest at 4.946 mi². Among places with at least 1,000 residents in 2020, Colusa city grew fastest since then (+1.8%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Colusa County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Colusa County is not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.

ZIP codes

9 ZIP Code Tabulation Areas have land in Colusa County; 7 of them have most of their land inside the county, and the others mainly cover neighboring areas.

956459591295932959509595595957959709597995987

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Colusa County

Colusa County shares a land border with 5 county equivalents. It has more land than 2 of them. The largest neighbor is Butte County (1,636.5 mi²) and the smallest is Sutter County (602.7 mi²). Together with its neighbors, Colusa County forms a block of 6,971.9 mi² of land, of which it holds 16.5%.

How big is Colusa County compared with U.S. states?

Colusa County has more land than 1 of the 50 states. It is about 1.1 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.7 times as much land (1,948.6 mi²). California’s county land could hold about 135 areas the size of Colusa County.

Another way to picture it: the same land area would fill a square about 33.9 miles (54.6 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Colusa County?

Colusa County has more land than 2,686 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Colusa County at #617 nationally by total area, 81 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 0.5%, compared with a national county-equivalent median of 1.2% — 0.7 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Colusa County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.