Thornton, CO -- U.S. city in Colorado Population (2000): 82384 Housing Units (2000): 29573 Land area (2000): 26.863620 sq. miles (69.576453 sq. km) Water area (2000): 0.335619 sq. miles (0.869249 sq. km) Total area (2000): 27.199239 sq. miles (70.445702 sq. km) FIPS code: 77290 Located within: Colorado (CO), FIPS 08 Location: 39.903043 N, 104.954406 W ZIP Codes (1990): 80229 Note: some ZIP codes may be omitted esp. for suburbs. Headwords: Thornton, CO Thornton