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Dog license's are to generate revenue for the town you lived in.
Rabies is often requested at CG's and in my experience more so if you stay at a state park. I've never been asked for the dog tag. They know that is a residential thing and you ARE traveling so it's a moot point!
Rabies shots can be got at any local vet in the town you are traveling in. Do take note that Some states differ in their requirements for how often the rabies shot is given. I've never had a CG question it. They just want to see the tag and/or certif.