where is lake shelbyville
â¢ Surface Area: 11,000 Acres. Lake Shelbyville is a reservoir located in Shelby County, Illinois and Moultrie County, Illinois created by damming the Kaskaskia River at Shelbyville, Illinois. The lake's normal surface pool is 11,100 acres (44.9 km2) at an elevation of 183 meters (600.4 ft).