Biked the Great Allegheny Passage a year ago last spring with two friends. It mostly follows abandoned railroad beds from Pittsburgh, Pennsylvania to Cumberland, Maryland. Absolutely beautiful scenery along the way, through the Laurel Highlands and the Ohiopyle State Park. Much of the route parallels rivers... the Monongahela, the Youghiogheny, the Casselman. We stayed in Pittsburgh right across the street from PNC Park, saw the Pirates play, then set off the next morning. We did about 50 miles a day, and stayed in B&Bs in Connellsville and Rockwood. The ladies were our support crew. They would sightsee during the day (Frank Lloyd Wright's Fallingwater is nearby), meet us for lunch, and drive ahead to our stopping point.
The first half is a barely noticeable uphill climb until about Ohiopyle, then it's a bit steeper climb to the Eastern Continental Divide just past Meyersdale. Near the Divide you go through the Big Savage Tunnel and after that its an exhilarating drop on the 27 miles to Cumberland, passing through Frostburg on the way. One day we'll lengthen the trip and continue from Cumberland down the C&O Canal into DC. And maybe do an autumn trip when the leaves are at their peak.