Alamosa County is a county in Colorado, United States, at the heart of the San Luis Valley. It had a population of 16,376 at the 2020 census and covers 723 square miles (1,870 km2) centred near 37°34′N 105°47′W.
Alamosa is the county seat and its postal code is 81101. The county has one city, one incorporated town, one census-designated place and several unincorporated communities. It observes Mountain Time and carries FIPS code 08003.
Towns & Villages in Alamosa County
Alamosa County has nine named places: a city, a town, one CDP, and six unincorporated communities scattered across the valley floor. Colorado has no civil townships, so places are listed without a township column. Unincorp. below means an unincorporated community with no municipal government.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| Alamosa | City · seat | 9,806 | 81101 |
| Hooper | Town | 108 | 81136 |
| Alamosa East | CDP | 1,376 | 81101 |
| Mosca | Unincorp. | — | 81146 |
| Estrella | Unincorp. | — | 81101 |
| Hartner | Unincorp. | — | 81101 |
| Henry | Unincorp. | — | 81101 |
| La Fruto | Unincorp. | — | 81101 |
| Waverly | Unincorp. | — | 81101 |
Alamosa East is a census-designated place directly adjoining the city of Alamosa on its east side and is often mistaken for a district of the city itself.
ZIP Codes
- 81101 — Alamosa (also serves Alamosa East, Estrella, Hartner, Henry, La Fruto and Waverly)
- 81102 — Alamosa (unique ZIP for a single large mail recipient)
- 81136 — Hooper
- 81146 — Mosca
Most of the county’s small unincorporated communities have no ZIP code of their own and receive mail through the Alamosa post office.
Geography
Alamosa County sits on the floor of the San Luis Valley, a broad, flat, high-desert basin ringed by the Sangre de Cristo Mountains to the east and the San Juan Mountains to the west. The Rio Grande crosses the county roughly west to east before bending south toward New Mexico. Elevations across the valley floor run around 7,500 feet, and the arid, sagebrush-covered terrain supports irrigated farmland fed by the river and groundwater wells. The county borders Saguache County to the north, Huerfano County to the east, Costilla County to the southeast, Conejos County to the southwest, and Rio Grande County to the west.
Demographics
Alamosa County’s population was 16,376 at the 2020 census, giving a density of about 23 people per square mile. Alamosa, the county seat, is by far the largest place with 9,806 residents, followed by the Alamosa East CDP at 1,376. Median household income in the county runs well below the Colorado median of $92,911, reflecting the valley’s agricultural, education and public-sector economic base.
Economy & Local Life
Adams State University, a public four-year school in Alamosa, is the county’s largest single employer and anchors the local economy alongside the San Luis Valley Health hospital system. Irrigated agriculture is central outside the city, with potatoes, barley, alfalfa and quinoa grown on the valley floor. Great Sand Dunes National Park and Preserve, partly in neighboring Saguache County, draws visitors through Alamosa as a gateway town, and the Rio Grande Scenic Railroad and San Luis Valley Regional Airport (with scheduled Denver service) both operate out of the county.
History
Alamosa County was organized on March 8, 1913, when the Colorado legislature carved it from the northwestern part of Costilla County. The name comes from the Spanish word for a grove of cottonwood trees, describing the stands of cottonwoods along the Rio Grande where the town of Alamosa was founded in 1878 as a Denver & Rio Grande Railway terminus. The railroad’s arrival made Alamosa the commercial hub of the San Luis Valley, a role it has kept since.
Getting There
U.S. Highways 160 and 285 cross at Alamosa, the county’s main road junction.
- Alamosa — county seat, at the U.S. 160/285 junction
- Del Norte, Rio Grande County — about 20 miles west via U.S. 160
- Monte Vista, Rio Grande County — about 15 miles west via U.S. 160
- Fort Garland, Costilla County — about 25 miles southeast via U.S. 160
San Luis Valley Regional Airport, just southeast of Alamosa, offers scheduled passenger service to Denver.
Frequently Asked Questions
Where is Alamosa County, Colorado?
It lies in south-central Colorado, in the San Luis Valley between the Sangre de Cristo and San Juan mountain ranges.
What is the population of Alamosa County?
16,376 people, per the 2020 census.
How big is Alamosa County?
723 square miles (1,870 km2), almost all of it land.
What is the county seat of Alamosa County?
Alamosa is the county seat.
How many towns and communities are in Alamosa County?
Nine named places: the city of Alamosa, the town of Hooper, the Alamosa East CDP, and six unincorporated communities.
What ZIP codes are in Alamosa County?
81101 and 81102 (Alamosa), 81136 (Hooper) and 81146 (Mosca).
What is Alamosa County named after?
The Spanish word “alamosa,” meaning a grove of cottonwood trees, describing the cottonwoods along the Rio Grande at Alamosa.
More counties in this state: Towns and villages in Colorado.