Scenery from Missouri. Castlewood state park in Autumn. This public park is located on 1401 Kiefer Creek Road, Ballwin, MO 63021. Between 1915 and 1940, thousands of St. Louis residents traveled by train each weekend to the Castlewood area for water fun, dancing and clubhouse partying. Today, the 1,802-acre Castlewood State Park preserves the history of the former resort. The park stretches for nearly five miles, straddling both sides of the Meramec River. It incorporates much of the old resort area, including the grand staircase that once led revelers up to the large hotels and clubs. Although the hotels and clubs are gone, the staircase and the lure of the region remain.