County Maps US

Costilla County, Colorado

A county in Colorado, ranked 55 of 64 by population.

CountyFIPS 08023

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

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Population
3,679
+180 (+5.1%) since 2020
Land area
1,228
square miles. A further 0.3% of the total area is water
Population density
3.0
people per square mile, computed rather than published
County seat
San Luis
Seat of county government.
Established
1861
164 years ago
Largest city
San Luis town
Population 597.

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 Costilla 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 Costilla 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 635 by 800 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 Costilla 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
Population3,67955th of 642,909th of 3,144
Land area1,228 sq mi38th of 64500th of 3,144
Population density3.0 per sq mi51st of 642,905th of 3,144
Median household income$36,86164th of 643,103rd of 3,143

Full data for Costilla County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population3,679Vintage 2025 Population Estimates
Population in 20203,499Vintage 2025 Population Estimates
2020 estimates base?3,494Vintage 2025 Population Estimates
Land area1,228 sq mi2025 Gazetteer Files
Water area3.4 sq mi2025 Gazetteer Files
Total area1,231 sq mi2025 Gazetteer Files
Population density?3.0 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$36,861American Community Survey 2020-2024 5-Year Estimates
Median home value$184,700American Community Survey 2020-2024 5-Year Estimates
Median age50.5American Community Survey 2020-2024 5-Year Estimates
Households1,651American Community Survey 2020-2024 5-Year Estimates
Housing units2,433American 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
-33
33 births, 66 deaths
Net migration
+39
More people moved in than moved out.

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

The 6 areas bordering Costilla 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
Huerfano CountyColorado54 mi7,011
Conejos CountyColorado35 mi7,529
Taos CountyNew Mexico28 mi34,564
Alamosa CountyColorado21 mi16,688
Las Animas CountyColorado21 mi14,391
Colfax CountyNew Mexico3.6 mi12,184

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.