Costilla County is a county in Colorado, United States, on the floor of the San Luis Valley against the New Mexico line. It had a population of 3,499 at the 2020 census and covers 1,227 square miles (3,180 km2) of land, centred near 37°17′N 105°26′W.
San Luis is the county seat, and its postal code is 81152. The county has 2 incorporated towns, 2 census-designated places, and several unincorporated communities. Costilla County is in the Mountain time zone.
Towns & Villages in Costilla County
Costilla County’s settlements sit mostly along the Culebra and Sangre de Cristo creek bottoms east of the Rio Grande. Only Blanca and San Luis are incorporated towns; Fort Garland and San Acacio are census-designated places (CDPs); the rest are unincorporated hamlets.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| San Luis | Town · seat | 629 | 81152 |
| Blanca | Town | 325 | 81123 |
| Fort Garland | CDP | 350 | 81133 |
| San Acacio | CDP | 29 | — |
| Chama | Unincorp. | — | 81126 |
| Garcia | Unincorp. | — | — |
| Jaroso | Unincorp. | — | 81138 |
| Mesita | Unincorp. | — | — |
| Russell | Unincorp. | — | — |
| San Pablo | Unincorp. | — | — |
| San Pedro | Unincorp. | — | — |
| Viejo San Acacio | Unincorp. | — | — |
San Acacio and Viejo San Acacio are two separate, closely spaced settlements on the Culebra — both are counted here rather than merged, since local usage keeps them distinct.
ZIP Codes
- 81152 — San Luis (also serves San Pablo, San Pedro, Viejo San Acacio)
- 81123 — Blanca
- 81133 — Fort Garland
- 81126 — Chama (post office box service)
- 81138 — Jaroso (post office box service)
San Acacio, Garcia, Mesita, and Russell do not have their own post office and are served by neighboring ZIP codes.
Geography
Costilla County lies on the eastern floor of the San Luis Valley, rising from irrigated bottomland along the Culebra and Rio Grande to the Sangre de Cristo Mountains on its eastern edge, including part of Blanca Peak, Colorado’s fourth-highest summit. The Rio Grande and Culebra Creek are the county’s principal waterways, and land use is split between dryland ranching, irrigated hay and alfalfa farming, and mountain forest.
Costilla County borders Alamosa County to the northwest, Huerfano County to the northeast, Las Animas County to the east, Conejos County to the west, Colfax County, New Mexico to the southeast, and Taos County, New Mexico to the south. Links: Alamosa County, Huerfano County, Las Animas County, Conejos County, and Colfax County, New Mexico.
Demographics
The 2020 census counted 3,499 residents, with San Luis (629) and Fort Garland (350) the two largest communities. Costilla County’s population is over half Hispanic or Latino, reflecting its roots as one of Colorado’s oldest Hispanic settlement areas. Median household income runs well below the Colorado median of $92,911, one of the lowest county figures in the state. Population density is about 2.8 people per square mile.
Economy & Local Life
Ranching, hay and alfalfa farming, and small-scale forestry anchor the local economy, alongside county and school-district government jobs. San Luis is home to the Sangre de Cristo Parish and the Stations of the Cross Shrine on the hill above town, a regional pilgrimage site. The San Luis People’s Ditch, the oldest continuously used water right in Colorado, still irrigates farmland along the Culebra.
History
Costilla County was organized November 1, 1861, as one of Colorado’s original 17 counties, formed under territorial law before Colorado achieved statehood. Its name comes from the Spanish word for “rib,” a reference to the ridge-like foothills along the valley’s eastern edge. San Luis, founded April 9, 1851, by settlers from Taos, New Mexico, is the oldest continuously occupied town in Colorado, predating the county itself by a decade. The Sangre de Cristo and Guadalupe land grants, dating to the Mexican era, shaped the county’s early common-land and acequia irrigation traditions, parts of which survive in local water law today.
Getting There
U.S. Route 160 crosses the county’s north end near Fort Garland, and State Highway 159 runs south from Fort Garland through San Luis to the New Mexico line.
- Alamosa — 40 miles northwest
- Walsenburg — 45 miles northeast
- Taos, New Mexico — 55 miles south
- Trinidad — 65 miles east
The nearest commercial airport is San Luis Valley Regional Airport in Alamosa.
Frequently Asked Questions
Where is Costilla County, Colorado?
In the San Luis Valley in south-central Colorado, bordering New Mexico to the south.
What is the population of Costilla County?
3,499 residents at the 2020 census.
How big is Costilla County?
1,227 square miles (3,180 km2) of land.
What is the county seat of Costilla County?
San Luis is the county seat and the oldest continuously occupied town in Colorado.
How many towns are in Costilla County?
Two incorporated towns (San Luis and Blanca), two CDPs (Fort Garland and San Acacio), and several unincorporated communities.
What ZIP codes are in Costilla County?
81152 (San Luis), 81123 (Blanca), 81133 (Fort Garland), 81126 (Chama), and 81138 (Jaroso).
What is Costilla County named for?
The Spanish word “costilla,” meaning “rib,” describing the ridge-like foothills along the valley’s east side.
More counties in this state: Towns and villages in Colorado.