Wyandot County is a county located in northwest Ohio, United States' As of the 2010 census, the population was 22,615. Its county seat is Upper Sandusky. It was named for the Wyandot Indians, who lived here before and after European encounter. Their autonym is variously translated from their language as "around the plains" and "dwellers on the peninsula". The county was organized by the state legislature from parts of Crawford, Marion, Hardin and Hancock counties on February 3, 1845.