Keywords: Guard Lock no 6 C and O Canal From NPS.jpg en Picture of Guard Lock 6 on the Chesapeake and Ohio Canal National Park Service from http //www hscl cr nps gov/insidenps/report asp STATE PARK CHOH STRUCTURE SORT RECORDNO 866 National Park Service Dept of Interior US Government Chesapeake Ohio Canal National Historical Park Locks water transport PD-USGov |