Nathrop is an unincorporated town, a post office, and a census-designated place (CDP) located in and governed by Chaffee County, Colorado, United States. The Nathrop post office has the ZIP code 81236. At the United States Census 2010, the population of the 81236 ZIP Code Tabulation Area was 1,017 including adjacent areas. History Nathrop was named for Charles Nachtrieb, owner of the townsite. In 1880, the Denver and Rio Grande Railroad built through Nathrop as part of their Tennessee Pass line. The tracks were placed out of service in 1997, but Union Pacific, present-day owner of the line, may reach an agreement to reopen it. Geography The Nathrop CDP has an area of , all land. Ruby Mountain Ruby Mountain is a rhyolite outcrop located about one mile northeast of Nathrop. Small spessartite garnet crystals are found throughout the outcropping. Small pebbles of black obsidian referred to as "Apache tears" by collectors can also be found in the talus rock at the base of the cliffs. Demographics The United States Census Bureau defined the for the Attractions Alpine Tunnel Arkansas Headwaters Recreation Area Browns Canyon National Monument Mount Princeton San Isabel National Forest St. Elmo See also Outline of Colorado Index of Colorado-related articles State of Colorado Colorado cities and towns Colorado census designated places Colorado counties Chaffee County, Colorado Arkansas Headwaters Recreation Area Browns Canyon National Monument References External links Nathrop @ Colorado.com Nathrop @ UncoverColorado.com History of Nathrop Arkansas Headwaters Recreation Area Browns Canyon National Monument Chaffee County website San Isabel National Forest website Census-designated places in Chaffee County, Colorado Census-designated places in Colorado Colorado populated places on the Arkansas River