County Maps US

Alamosa County, Colorado

A county in Colorado, ranked 30 of 64 by population.

CountyFIPS 08003

Within Colorado
Alamosa County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Alamosa, the county seat, located via the 2025 Census Gazetteer.

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Population
16,688
+311 (+1.9%) since 2020
Land area
722.6
square miles. A further 0.1% of the total area is water
Population density
23.1
people per square mile, computed rather than published
County seat
Alamosa
Seat of county government.
Established
1913
112 years ago
Largest city
Alamosa city
Population 9,849.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Alamosa County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Alamosa County, Colorado from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 800 by 694 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Alamosa County ranks

Position among the 64 counties of Colorado, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn ColoradoNationally
Population16,68830th of 641,995th of 3,144
Land area722.6 sq mi53rd of 641,232nd of 3,144
Population density23.1 per sq mi21st of 642,124th of 3,144
Median household income$55,39751st of 642,444th of 3,143

Full data for Alamosa County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population16,688Vintage 2025 Population Estimates
Population in 202016,377Vintage 2025 Population Estimates
2020 estimates base?16,378Vintage 2025 Population Estimates
Land area722.6 sq mi2025 Gazetteer Files
Water area0.65 sq mi2025 Gazetteer Files
Total area723.3 sq mi2025 Gazetteer Files
Population density?23.1 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$55,397American Community Survey 2020-2024 5-Year Estimates
Median home value$239,100American Community Survey 2020-2024 5-Year Estimates
Median age33.2American Community Survey 2020-2024 5-Year Estimates
Households6,648American Community Survey 2020-2024 5-Year Estimates
Housing units7,241American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
-2
175 births, 177 deaths
Net migration
0
Arrivals and departures balanced.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 5 areas bordering Alamosa County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Saguache CountyColorado32 mi6,732
Rio Grande CountyColorado24 mi11,087
Costilla CountyColorado21 mi3,679
Conejos CountyColorado19 mi7,529
Huerfano CountyColorado14 mi7,011

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

All 64 counties of Colorado

Open the interactive Colorado county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.