Yuma is a home rule municipality that is the most populous municipality in Yuma County, Colorado, United States. The population was 3,456 at …Yuma is a home rule municipality that is the most populous municipality in Yuma County, Colorado, United States. The population was 3,456 at the 2020 census. A post office in Yuma has been in operation since 1885. The community was named after a Native American named Yuma who worked for the railroad, died and was buried near the town site.