Take A Trip into Yesteryear! The Keystone Historical Museum is housed in the Keystone Schoolhouse building of early Victorian architecture built in 1899. The Museum houses early day mining tools, historic pictures and photo collections, rock and mineral collections, and historic displays including Carrie Ingalls (of Little House on the Prairie fame) memorabilia.
https://www.keystonehistory.org
410 3rd St, Keystone, SD 57751