Marysville is a city in Union County, Ohio, United States. It is the county seat of Union County. The population was 15,942 at the 2000 census, and the Census Bureau estimated 17,621 in 2006. In 2006, Marysville was named one of the best five hometowns in Ohio by Ohio Magazine. The City is building new sewer facilities and a water reservoir which will prepare the community for future growth, as Union county is currently the third fastest growing county in the state of Ohio. Marysville’s "Uptown Area" (downtown) has recently experienced large investment by the public-private partnership group "Uptown Renewal Team" (URT), and over $1,000,000 has recently been invested by various business owners. Marysville's longtime slogan is "Where the Grass is Greener".