Dolliver Memorial State Park in central Iowa preserves a striking river landscape of high bluffs, ravines, and narrow canyons along the Des Moines River, where erosion has exposed notable sandstone and the Copperas Beds, a mineral-rich outcrop with iron sulfate formations rare in Iowa. The area also holds older human history, including Native American mounds and evidence that Boneyard Hollow may have been used in bison hunting. Interest in protecting the land grew after the 1915 Hennepin Plate hoax drew attention to its scenery, leading to its purchase and dedication in 1925 as Iowa’s third state park. New Deal crews later built many of its rustic park structures.