Mason City is a city in Cerro Gordo County, Iowa, United States. The population was 29,172 at the 2000 census and has stayed close to 30,000 since 1995. It is the county seat of Cerro Gordo County. North Iowa Area Community College and Hamilton College are located here. Mason City is the birthplace and childhood home of composer and playwright Meredith Willson. The fictional city of River City, Iowa in his musical The Music Man is loosely based on Mason City. Willson's birthplace has been restored as a tourist attraction and is part of the Music Man Square complex that includes a plaza with a bronze statue of Willson in a band major's uniform.

Puppeteer Bil Baird grew up in Mason City; his creations were featured in The Sound of Music and are now exhibited at the MacNider Art Museum. Also from Mason City were book designer, author and concert impresario Merle Armitage; and Steven Clay, publisher of Granary Books (New York). After a concert at the Surf Ballroom in nearby Clear Lake, IA on the night of February 3, 1959, Buddy Holly, Ritchie Valens and the Big Bopper died in a plane crash after taking off from the Mason City Municipal Airport. Mason City is widely known for its sizable amount of Prairie School architecture, the largest concentration in one location outside of Oak Park, Illinois. The Rock Glen and Rock Crest districts along Willow Creek feature homes designed by Frank Lloyd Wright and Walter Burley Griffin. Wright's Stockman House has been restored and is open to the public. Also, Wright's Park Inn Hotel, which influenced Bauhaus founder Walter Gropius and other European Modern architects, and which is the only remaining hotel in the world designed by him still standing, is in the process of being restored.