on the National Register of Historic Places in Washington, D.C. Chesapeake and Ohio Canal Cumberland, Maryland Historic districts in Morgan County, West Virginia Journey Through Hallowed Ground National Heritage Area Long-distance trails in the United States National Historical Parks of the United States National Park Service areas in Washington, D.C. National parks of the Appalachians National Register of Historic Places in Allegany County, Maryland National Register of Historic Places in Frederick County, Maryland National Register of Historic Places in Washington County, Maryland National Register of Historic Places in Morgan County, West Virginia Parks in Allegany County, Maryland Parks in Cumberland, MD-WV-PA Parks in Frederick County, Maryland Parks in Montgomery County, Maryland Parks in Washington County, Maryland Parks in Washington, D.C. Parks on the National Register of Historic Places in Maryland Parks on the National Register of Historic Places in Virginia Parks on the National Register of Historic Places in Washington, D.C. Parks on the National Register of Historic Places in West Virginia Protected areas established in 1938