3 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| San Luis | 1 | 635 | 602 | 1.11% | 1,120 | 0.57 | Town |
| Fort Garland | 2 | 619 | 607 | 1.98% | 1,646 | 0.38 | CDP |
| Blanca | 3 | 344 | 323 | 1.18% | 188 | 1.83 | Town |
San Luis is the largest city in Costilla County, with a population of 635.
Blanca is the smallest city in Costilla County.
There are 3 cities in Costilla County, Colorado.