Founded on 1861-11-01, Costilla County is one of 64 counties in the state of Colorado. Historically, Costilla County was formed from Created as one of the 17 original counties of the Territory of Colorado. The city of San Luis is the county seat. With FIPS code of 23, Costilla County has a population of 3,625 and area of 1,229.38 square miles (3,184 km2).
List of all cities in Costilla County, CO alphabetically
| City/Town | Postal Code | Area Code |
| Blanca, CO | 81123 | 719 |
| Chama, CO | 81126 | 719 |
| El Rito, CO | 81152 | 719 |
| Forbes Park, CO | 81133 | 719 |
| Fort Garland, CO | 81133 | 719 |
| Garcia, CO | 81152 | 719 |
| Jaroso, CO | 81138 | 719 |
| Los Fuertes, CO | 81152 | 719 |
| Mesita, CO | 81152 | 719 |
| San Francisco, CO | 81152 | 719 |
| San Luis, CO | 81152 | 719 |
| San Pablo, CO | 81152 | 719 |
| San Pedro, CO | 81152 | 719 |
| Sangre de Cri, CO | 81133 | 719 |
| Sangre de Cristo Ranches, CO | 81133 | 719 |
| Wildhorse Mesa, CO | 81152 | 719 |