myownlittleworld from PA on 7/11/2013 9:27:45 PM:
Ok, I just tried to reply, so if this ends up being a double post, ...sorry.
Go to http://www.atatrail.org/tmi/maps.cfm to find a break down by map of camping available. There are some (although not as many as the C&O). I know that one is 28 miles out from Pittsburgh, then it goes to appx. 39 & 51 miles out. They are supposed to be on, or very near, the trail. The last one is the Outflow camping area below Ohiopyle state park. That one is back from the trail a bit, as I understand.
That is it for the "gratis" campsites. If the interest in that type of site is generated by cost, Rockwood shows a paid site right on the trail for 10pp if I recall correctly. I hear that the YMCA in Cumberland allows tents for 10, but I am not sure if it was per person, or per tent (as it was described to me).
(Unverified, as of yet, ...I am planning my own trip for August, and this is what I have determined.)