We pull a 34' 5th wheel and routinely camp at Apgar. Of course, many sites are not big enough, but there are enough that are. I believe you can go as far up Going to the Sun Road as Avalanche Lake Campground with a big rig, but beyond there vehicles are limited to 21' bumper to bumper.
I don't believe so, there may be a few sites that will not work for large RVs. I really enjoyed staying there, I hope you do too.
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