Googled: the GAP in Pittsburgh
yields: http://www.atatrail.org/[/URL]
"Welcome ....the Great Allegheny Passage (GAP) rail-trail offers 141 miles of hiking and biking between Cumberland, MD,
and Homestead, PA, near Pittsburgh. In Cumberland, the GAP joins the C&O Canal Towpath, creating a continuous trail experience, 325 miles long, to Washington, DC. The final mile from Homestead to Pittsburgh is still under construction. Check
Trail Construction Status for updates."