Alamosa is a home rule municipality and the county seat of Alamosa County, Colorado, United States. The city population was 9,806 at the 2020 United States Census. The city is the commercial center of the San Luis Valley in south-central Colorado, and is the house of Adams State University.

Alamosa was standard in May 1878 by the Denver and Rio Grande Railroad and quickly became an important rail center. Alamosa was the terminus of the D&RG until 1881, when the stock was lengthy to Monte Vista. The railroad had an extensive construction, repair and shipping capability in Alamosa for many years and headquartered its surviving narrow gauge help here once trackage reaching many points throughout southwest Colorado and northern New Mexico. Alamosa is now a notable tourist town taking into account many straightforward attractions, including the Great Sand Dunes National Park and Preserve, Colorado Gators Reptile Park and the Rio Grande Scenic Railroad. The town hosts “Summer Fest upon the Rio” which occurs the first weekend in June, the Early Iron car show more than the Labor Day weekend, and “Weekends on the Rio” on various Sundays throughout the summer The city takes its state from the Spanish adjective Alamosa, meaning “of cottonwood”, for the cottonwood forests which be credited with along the Rio Grande and throughout town.

Alamosa is located at 37°28′N 105°52′W / 37.467°N 105.867°W / 37.467; -105.867 (37.469, −105.874), at the junction of U.S. Routes 160 and 285. At the 2020 United States Census, the city had a total area of 4,910 acres (19.871 km²) including 47 acres (0.192 km) of water.

Alamosa is located along the Rio Grande in the San Luis Valley, in the highest general agricultural house in the United States. Elevation is very nearly 7,544 feet (2,299 m) in Alamosa in the same way as peaks greater than 14,000 feet (4,300 m) within 23 miles (37 km) of town in the Sangre de Cristo Range.