Alamosa is a city under Home Rule Municipality that is the county seat and the most populous municipality of Alamosa County, Colorado, United States. The city population was 8,780 at the 2010 United States Census. The city is the commercial center of the San Luis Valley in south-central Colorado, and is the home of Adams State University.
Alamosa was established in May 1878 by the Denver and Rio Grande Railroad and quickly became an important rail center. The railroad had an extensive construction, repair and shipping facility in Alamosa for many years and headquartered its remaining narrow gauge service here with trackage reaching many points throughout southwest Colorado and northern New Mexico. Alamosa is now a notable tourist town with many nearby attractions, including the Great Sand Dunes National Park and Preserve and Colorado Gators Reptile Park. The town hosts "Summer Fest on the Rio" which occurs the first weekend in June, the Early Iron car show over the Labor Day weekend, and "Weekends on the Rio" on various Sundays throughout the summer The city takes its name from the Spanish adjective Alamosa, meaning "of cottonwood", for the cottonwood forests which grow along the Rio Grande and throughout town.
Alamosa is located at 37°28′N 105°52′W (37.469, −105.874), at the junction of U.S. Routes 160 and 285. According to the United States Census Bureau, the city has a total area of 5.5 square miles (14.3 km2), of which 5.4 square miles (14.0 km2) is land and 0.12 square miles (0.3 km2), or 2.26%, is water.
Alamosa is located along the Rio Grande in the San Luis Valley, in the highest general agricultural land in the United States. Elevation is about 7,544 feet (2,299 m) in Alamosa with peaks over 14,000 feet (4,300 m) within 23 miles (37 km) of town in the Sangre de Cristo Range.
Alamosa is the gateway city to the Great Sand Dunes National Park and Preserve.