I mtn. biked & camped the GRT in West Virginia for 3 nights 4 days.
The campsites have a picnic table & fire ring, some have a well pump, and 2 have 3-sided shelters. The campsites are all in the trees & have enough trees to hammock there. All are right next to the rail trail. Its peacefull and not crowded at the campsites. The trail is mostly shaded.
Choose your sites carefully for pump water and how close to the river you are. MP 28 campsite has 2 rope swings too. Swimming is mandatory.

I could have brought a lot less food. Marlington is Milepost 55 and was a good stop for lunch or dinner. (I stopped in during 'Pioneer Days' street fair & had an all-you-can-eat spaghetti dinner). A store @ MP 45 has drinks, beer, snacks, & makes pizza & sandwiches.

At MP 80 is Cass Scenic Railroad - you can ride the train up the mtn.

There are so many options of start & end points to choose from.
But be forwarned - NO CELLPHONE SERVICE.