Chesapeake & Ohio Canal National Historic Park
Annual visitors: 4.8 million
Location: Hagerstown, Md.
Size: 185 miles
Founded: 1938
Highlights: The C&O Canal began as a way for communities along the Potomac River to transport lumber, coal and other products. VIsitors can now ride in a replica boat drawn by mules, which historically tugged the boats since they were heartier and cheaper than horses.
