Great tip and info and a direct answer to your question.

Entirely different line:
I like to ride out of our dense then sprawling Southern cities w/o long range bicycle infrastructure during the late night and wee morning hours. Best time to avoid the drunks and morning rush. Makes it much easier to punch outside of cities like Austin, San Antonio, Houston, Dallas, Memphis, etc… And Pittsburgh is different, with the Montour trail connection from the airport to the GAP on down to DC. Soon to be up to Eerie as well, I understand… And DC also has a direct bike trail to Ronald Reagan airport and Amtrak at the other end.
So,
Could consider moving through Pittsburgh at night. Maybe stop and rest at the Dravo Cemetery, a very cool place to camp. You move through some of the least scenic areas in the dark this way anyway. But best part is, you get to sleep in a very old cemetery ! It is also too close to Pittsburgh to stop and camp if you leave out in the am. Easier to time Dravo on the return up to Pittsburgh, for most folks. But you get in at midnight and may feel like riding there.

If you do stay overnight in Pittsburgh, the Adirondack shelters/park/grocery store in Connellsville is a Very Nice spot to camp. You can network a bit with other GAP riders and community members and provision as needed at the grocery and liquor stores in front of the shelters and train caboose.

Highly recommend Husky Haven in Rockwood, Trail Inn Bed/Breakfast/Campground in Frostburg, Md, C&O Bicycles and Bunkhouse in Hancock, Md.
Lots of stops with things to see, do, take in, along the entire GAP/C&O.
Have fun !