Mason City, United States

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, a decline from 29,172 in the 2000 census. The Mason City Micropolitan Statistical Area includes all of Cerro Gordo and Worth counties. It is commonly referred to as the "River City", as the city grew up centered on the Winnebago River.

The region around what would later be first called Shibboleth was a summer home to the Sioux and Winnebago nations. The first settlement that became Shibboleth was established in 1853 at the confluence of the Winnebago River and Calmus Creek. The town had several names: Shibboleth, Masonic Grove, and Masonville until Mason City was adopted in 1855, in honor of a founder's son, Mason Long.