Shiawassee is a county located in the U.S. state of Michigan. As of the 2010 census, the population was 70,648. The county seat is Corunna. The county was founded in 1822 and organized in 1837. Shiawassee County is named for the Shiawassee River, and means ‘river that twists about’. In 2010, the center of population of Michigan was located in Shiawassee County, in the township of Bennington.