Just don't go to the Charlotte post offices for a passport. I spent hours at 2 different ones and they closed the office on me both times for either lunch or because it was the end of the day. Very incompetent procedure.
I ended up going to Gastonia and was in and out in 15 minutes. I don't know about Rock Hill.
It is not just any location that will process them though - here are the locations you need.
Where to Apply for a Passport Nationwide
You can download the forms and save yourself some time.