Alamosa County area

Population and density of Alamosa County

The Census Bureau estimates that 16,688 people lived in Alamosa County on July 1, 2025. That ranks #2,058 of 3,222 county equivalents nationally and #30 of 64 in Colorado. Since the April 1, 2020 estimates base of 16,378, the population has grown by 310 (+1.9%), compared with +4.1% for Colorado as a whole.

With 722.6 square miles of land, that is 23 people per square mile (8.9 per km²), placing Alamosa County #2,204 nationally for density and #21 in Colorado. The median county equivalent has 47 people per square mile; the Colorado median is 11. Put another way, there are about 28 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 Alamosa County

2 incorporated places lie at least partly in Alamosa County. Together they are home to 9,926 people (59.5%); the other 6,762 (40.5%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Alamosa city, with 9,849 residents in the county.

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

Metropolitan area

Alamosa County is a central county of the Alamosa, CO Micropolitan Statistical Area. Its 3 county equivalents have 27,896 residents on 3,237.7 square miles of land; Alamosa County accounts for 22.3% of the land and 59.8% of the residents. By combined land it ranks #44 of 542 micropolitan areas, and #456 by population.

ZIP codes

5 ZIP Code Tabulation Areas have land in Alamosa County; 3 of them have most of their land inside the county, and the others mainly cover neighboring areas.

8110181125811368114481146

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 Alamosa County

Alamosa County shares a land border with 5 county equivalents. Each of them has more land than Alamosa County. The largest neighbor is Saguache County (3,168.6 mi²) and the smallest is Rio Grande County (912 mi²). Together with its neighbors, Alamosa County forms a block of 8,909.2 mi² of land, of which it holds 8.1%.

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

Alamosa County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.4 times as much. Colorado’s county land could hold about 143 areas the size of Alamosa County.

Another way to picture it: the same land area would fill a square about 26.9 miles (43.3 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 Alamosa County?

Alamosa County has more land than 1,990 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 Alamosa County at #1,345 nationally by total area, 113 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 0.1%, compared with a national county-equivalent median of 1.2% — 1.1 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 Alamosa 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.