Warren County, OhioForest, Flowers, Falls and Fossils This 278-acre preserve holds a mature deciduous forest with a large variety of spring wildflowers and ferns. An old field habitat also sustains a variety of species. Halls Creek and Grays Run pass through the preserve, forming small waterfalls as they flow over fossil-rich Ordovician bedrock. Two miles of trails wind through the property between the two creeks. Protected by Ohio Department of Natural ResourcesThe ODNR Division of Natural Areas and Preserves operates and maintains the preserve. Interested in volunteering? Click here for more information. | How to Find Halls Creek WoodsThe preserve parking area is located on Mason-Morrow-Millgrove Road (County Road 38) three miles east of South Lebanon and three miles west of Morrow. |