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is a census-designated place (CDP) in Douglas County, Colorado, United States. The population was 70,931 at the 2000 census; it is one of the most populous unincorporated communities in the United States. The Littleton Post Office (ZIP Codes 80126, 80129, 80130, and 80163) serves Highlands Ranch.
According to the United States Census Bureau, the CDP has a total area of 23.5 square miles (61.0 km²), of which, 23.5 square miles (60.9 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.09%) is water.