The bricks used in building Fort Ridgely were made about a quarter of a mile northeast of the fort, from a bed of clay, perhaps of Cretaceous age, in the west bluff of Fort creek. (A Report on the Geological and Natural History Survey of Minnesota, Volume II, 1882-1885, N. H. Winchell and Warren Upham, Pioneer Press Company, St. Paul, Minnesota, 1888, Page 179)