The combined value of farms, ranches, and rural real estate for sale in Clay County recently on Land.com was $9 million. This represents approximately 1,000 acres of farms, ranches, hunting land and other land for sale in Clay County. Clay County ranks 16th out of 66 counties in the Coyote State for the total acreage of land currently advertised for sale. Vermillion had the most land for sale. From an economic perspective, government and state-level services contribute most to Clay County's overall GDP. Clay County is South Dakota's 66th biggest county (417 square miles). It's located in the Southeast South Dakota region of South Dakota.