Powderhorn is an unincorporated community and a U.S. Post Office in Gunnison County, Colorado, United States. The Powderhorn Post Office has the ZIP Code 81243.A post office called Powderhorn was established in 1880. Some say the community was named from a nearby landform in the shape of a powderhorn, while others believe an old powderhorn found near the town site caused the name to be selected.