Originally Posted by Rpatrick16
The suggestion that GLCMRANGER made is a great one. Actually, you can't take a trailer beyond the Apgar point.... Welcome to Montana!
All good suggestions but you actually CAN take a trailer beyond Apgar.
Depending on the size of your rig you can go (take a trailer) all the way to Avalanche Campground on the West Side - Apgar Campground has good sites - like most Park campgrounds there are no hookups and it's first come/served. But you can usually find something unless later in the day. Fish Creek a couple miles from the West Entrance is reserveable - that might be what one of the other posters meant by "Big Creek" but some of the sites are tight.
Outside the park on the west side: The KOA is good, but a little more pricey - the Glacier Campground has all the hookups and less so, San-Suz-Ed nice but between the two in price and right on the road. There are other more expensive places and they do fill up.
"Best" is a relative term! Have fun - spend some time. You will miss a lot if you're there only one or two nights.
Then, there is the whole east side.