Mason City is a city in 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 theatre heritage, serving as the inspiration for the town of “River City” in The Music Man. It is also a historic industrial center for brick and cement production, and is home to a significant collection of Prairie School style architecture. Along with nearby Clear Lake, the city forms a regional commercial, industrial, and cultural hub for north-central Iowa.