The City of Gunnison is the county seat and the most populous municipality of Gunnison County, Colorado, United States. As of the 2010 census, the city had a population of 5,854. It was named in honor of John W. Gunnison, a United States Army officer who surveyed for the transcontinental railroad in 1853. Gunnison is a Home Rule municipality which reserves the right to choose how it is governed.