Waseca County is a county in the U.S. state of Minnesota. As of the 2020 census, the population was 18,968. Its county seat is Waseca. In 1849, the newly organized Minnesota Territory legislature authorized nine counties across the territory. One of those, Dakota, was partially subdivided in 1853 to create Blue Earth, Le Sueur, and Rice counties. In 1855, parts of t…Waseca County is a county in the U.S. state of Minnesota. As of the 2020 census, the population was 18,968. Its county seat is Waseca. In 1849, the newly organized Minnesota Territory legislature authorized nine counties across the territory. One of those, Dakota, was partially subdivided in 1853 to create Blue Earth, Le Sueur, and Rice counties. In 1855, parts of those counties were partitioned to create Steele. On February 27, 1857, the territorial legislature authorized partitioning western Steele County to create Waseca County, with its seat at Wilton, a settlement which began in 1854. The county name was taken from the area's first farming settlement, started in 1855, near the present location of the city of Waseca. That settlement name came from the Dakota word meaning "rich," a reference to the fertile soil in the area.