Mason City is a city and the county seat of Cerro Gordo County, Iowa, United States. The population was 27,338 in the 2020 census. Mason City is known for its musical heritage, high concentrations of renowned Prairie School style architecture, and a close connection with nearby Clear Lake. The Mason City Micropolitan Statistical Area includes all of Cerro Gordo and Worth counties. Local institutions of higher education include North Iowa Area Community College.