Grayson Lake is a 1,500-acre reservoir in Carter and Elliott counties in Kentucky. It was created by the United States Army Corps of Engineers in 1968 by impounding the Little Sandy River with the Grayson Dam, an earthen structure 120 feet high, creating a maximum capacity of 118,990 acre-feet. Sections of Kentucky Route 7 were re-routed as a result of …Grayson Lake is a 1,500-acre reservoir in Carter and Elliott counties in Kentucky. It was created by the United States Army Corps of Engineers in 1968 by impounding the Little Sandy River with the Grayson Dam, an earthen structure 120 feet high, creating a maximum capacity of 118,990 acre-feet. Sections of Kentucky Route 7 were re-routed as a result of the lake's creation. KY 7 now traverses a modern highway stretch around the park, crossing the dam also.