Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Cerro Gordo County is a county located in the U.S. state of Iowa. The population was 44,151 in the 2010 census, a decline from 46,447 in 2000. Its county seat is Mason City. The county is named for the Battle of Cerro Gordo, which took place during the Mexican-American War. Cerro Gordo County is part of the Mason City Micropolitan Statistical Area. According to the 2000 census, the county has a total area of 575.12 square miles, of which 568.33 square miles is land and 6.80 square miles is water.