Hamilton City (formerly, Hamilton) is a census-designated place (CDP) in Glenn County, California, United States. The population was 1,903 at the 2000 census. Hamilton City is located 9.5 miles (15 km) east of Orland, at an elevation of 151 feet (46 m). The default numbers used for wired telephones in Hamilton City are (530) 826-xxxx. The postal ZIP Code is 95951.