A timbered recreation area, it was named for rainbows which form in the falls under certain light conditions. A local story states has that it was named by George Onn of Dryad, for the Rainbow Division, which participated in World War I. The park features shoreline on the Chehalis River and 120-acres of old-growth timber. Five miles of shady trails wind through the park. A 200-foot cable footbridge, suspended over the river, leads into a forest wilderness. Improvements to the park were done as part of a Civilian Conservation Corps project in the 1930s.