Allegany is a huge park with 2 campgrounds, Quaker and Red House which are a 45 minutes drive apart. Each campground is near a small lake, and each has a beach within a short driving distance from the campsites.
Quaker Beach
Quaker is a bit more out of the way than Red House but has larger sites with more buffer between them than Red House. There are many great large/deep private sites at Quaker, as well as newer bathrooms in Loop B. Lots of sites are up along the side of a hill so entry ways can be a bit more challenging for those with trailers. Lower sites (Cain Hollow Loop B) are more level than the other loops. Cain Hollow Loop A is in an open field on the side of a hill with few trees. The beach requires driving too but is quite nice with modern facilities.
Red House Beach
Red House is a busier campground than Quaker with smaller sites and less buffer between neighbours. Consider this area more social than the private sites of Quaker. Sites at Red House are much more level with easier access than many of the sites at Quaker. Red House Loop A sites are in the open and very close together. The beach is a short distance but still requires driving too and features canoe, kayak and paddle boat rentals. Several historic buildings in and around the Red House area.