Just before covid/18months ago? Herr's Tavern (now apparently "Inn at Herr's Ridge") had 2 bar boxes in the bar. Couple miles out of town but still on battlefield. You probably won't find anyone playing, though, maybe a couple on a date. I would definitely check before going out, Covid has changed everything everywhere, and they certainly don't feature the bar, or tables, on the current website. Nice enough place to eat, but there are just as good/better in town.
Ott House in Emmitsburg, MD (12 miles?) has always been pool friendly. Again, before covid, call and check. 3 barboxes, used to be maintained by a friend of mine, but that was,...let's see.... oh heck, 1970 through 1980's.
FEMA campus is there, so between locals and visitors there is often a game to be had, sometimes challenge table, depending on night. OTOH, it can be impossible to get seated for dining some weekday nights, though the bar is long, capacious and friendly. Have also been in when the pool section was dead, too, in recent years.
40 years ago could have told you bar tables all over that area Mason-Dixon line. & non-stop barbox action, if you wanted it. Mostly cheap games by the game, but high$$ sets available by arrangement. Can't recall any big tables. Most barboxes have now been removed for more higher end restaurant/bar seating. Many like the Logs (Lincoln Logs), Blue Duck, Track Inn have been closed, converted to residential, or become re-incarnated as higher end restaurants. The actual Gettysburg pool hall closed in the early 70's and is now something like a gallery or photo shop, IIRC.
Frederick, MD (35 miles?) has a couple, maybe 3 pool halls. (3 or 4 years ago) Check hours, what has happened with Covid, etc.
Grew up that area, moved upstate NY 30 years ago. Still go down some years for work in DC, but am aging out of that, too.
Have fun!
smt
PS: dunno what your other interests are, but Eastern Museum of Motor Racing is not far out of town toward Harrisburg, off the highway in York Springs. For a small out of the way museum, they have an interesting collection. For years, a Miller was in the lobby. Not sure if on loan or owned. Lots of other rare engine stuff. Hours can be a little variable, so again, "check before heading out".
https://emmr.org/