Of 102 counties in the Prairie State, Clay County is 60th in terms of its size (469 square miles). Clay County is in Southern Illinois. Clay County, Illinois, has roughly 1,000 acres of riverfront homes and property for sale based on recent Land Network data. The combined market value of land for sale here was approximately $2 million. Browse all waterfront property for sale in Clay County on the Land Network to find the marina, lakefront and other recreational property that meets your needs, from waterside land perfect as a retirement investment to existing residential waterfront land and property for hunting, fishing and other outdoor-recreation pursuits! The most common type of land for sale by combined acreage in Clay County is house.