Costilla County, Colorado
County seat: San Luis · Population 3,679 (2025) · 1,228 sq mi
Costilla County is the 55th most populous of Colorado's 64 counties, with 3,679 people (2025 estimate). Its county seat is San Luis. It is part of the Region 8: San Luis Valley region, one of the 14 Planning and Management Regions of Colorado. The map shows its 2 cities and towns and the 6 neighboring counties.
Costilla County facts
- County seat
- San Luis
- Population (2025 estimate)
- 3,679 +5.3% since 2020
- Land area
- 1,228 sq mi 38th largest of 64
- Water area
- 3 sq mi
- Population density
- 3 per sq mi
- Established
- 1861
- Largest city
- San Luis 597
- Median household income
- $36,861
- Cities and towns
- 2 plus 2 CDPs
- ZIP codes
- 7
- Time zone
- Mountain
- FIPS code
- 08023
Cities and towns in Costilla County
Costilla County has 2 incorporated cities, towns and villages. Populations count the people living inside Costilla County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| San Luis (county seat) | Town | 597 | |
| Blanca | Town | 320 |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| Fort Garland | 446 | |
| San Acacio | 61 |
ZIP codes in Costilla County
7 ZIP codes reach into Costilla County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 81055 also Huerfano County
- 81123
- 81126
- 81133
- 81138
- 81151 also Conejos County
- 81152
Population of Costilla County, 2020–2025
Costilla County grew by 185 people (+5.3%) between April 2020 and July 2025: 125 more deaths than births and a net gain of 314 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 3,499 |
| 2021 | 3,607 |
| 2022 | 3,602 |
| 2023 | 3,618 |
| 2024 | 3,673 |
| 2025 | 3,679 |
Neighboring counties
- Huerfano County northeast · 7,011 people
- Conejos County west · 7,529 people
- Taos County, New Mexico south · 34,564 people
- Alamosa County northwest · 16,688 people
- Las Animas County east · 14,391 people
- Colfax County, New Mexico southeast · 12,184 people
Printable Costilla County map
The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.
- PDF (Letter) (75 KB)
- PNG (2400 px) (80 KB)
Paste this code to embed the map on your site:
Sources
- Boundaries: U.S. Census Bureau, 2025 Cartographic Boundary Files (1:500,000).
- Population: Census Bureau county and city estimates, Vintage 2025. CDP populations: American Community Survey 2020–2024.
- Places and ZIP codes: Census Bureau 2026 Gazetteer and 2020 ZIP Code Tabulation Area relationship files.
- County seat, founding year and name origin: Wikidata (CC0), checked against state sources.
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