Nebraska's newest state park. A national historic bridge across the Niobrara River provides access for visitors to walk to our state's highest waterfall. The Jim MacAllister Nature Trail alerts hikers to diverse ecological sytems in the valley that exist nowhere else in North America. Office open Memorial Day-Labor Day, Mon-Thu & Sun, 8am-10pm; Fri-Sat, 8-11am. Park permit required. Fee for camping. Partial Handicapped Accessibility.