It depends on how you like to camp. If you prefer dry camping which I do, I like 2 medicine GC inside Glacier NP at the east entrance, I have camped there at least 3 times over the years and twice got a site right on the lake. Caught some nice trout there also(you don't need a license to fish in the park). Camped at the west side also at St Mary's was nice but preferred the east side, less crowded. If you can get into Custer State park that would be great stayed there once years ago but could not get a site in recent years so we stayed at Wind Cave NP CG. Visited the cave drove through Custer and visited Mount Rushmore from there. The CG's and the cave tour was half price if over 62 and get the senior pass, Custer was not. I never made reservations ahead of time because things change if you have limited time you will need reservations at Custer if you want to stay inside.
