There are 8 US Post Offices in Gunnison County serving a total of 13,345 residents equating to 1,668 residents per post office. It's estimated that approximately 21,300 packages are handled across the 8 county post offices annually. Gunnison County is the fifth-most extensive of the 64 counties in the U.S. state of Colorado. As of the 2010 census, the population was 15,324. The county seat is Gunnison. The county was named for John W. Gunnison, a United States Army officer and captain in the Army Topographical Engineers, who surveyed for the transcontinental railroad in 1853. Daniel I.J. Thornton, the Republican governor of Colorado from 1951 to 1955, operated a ranch in Gunnison County. The city of Thornton, Colorado, north of Denver, is named in his honor."