This report presents the results of research on the conditions of formal and informal (visitorcreated) trails conducted within the Great Falls Park (GFP) portion of George Washington Memorial Parkway (GWMP), Virginia, and the adjacent Maryland portions of the C&O Canal National Historical Park (CHOH). This research was prompted primarily by concerns about the impact of extensive informal trail networks within both parks on native vegetation and rare plant communities, rare flora and fauna, and historic and archaeological resources. Resource conditions on formal park trails were also assessed to provide information supporting the development of park planning and management decision-making.