Worth County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 7,598. The county seat is in Northwood. The county was founded in 1851 and named for Major General William Jenkins Worth (1794–1849), an officer in both the Seminole War and the Mexican-American War.Worth County is part of the Mason City, IA Micropolitan Statistical Area.