Google "Crossing the border into the US". Lots of reading, but you'll save time in the long run. You may be asked a question or two at the border. Whatever you do, don't lie. They most likely already know the answer. When I was crossing northbound at Sweetwater MT. headed for Alaska, I handed my passport to the attendant. He asked me if I'd ever been fingerprinted. I said, "Maybe when I joined the Navy but I don't remember." DUH. My fingerprints were on the passport he was looking at.
There was a Canadian heading southbound at the same time and place. He was busy putting everything from his RV that wasn't permanently attached on a blanket on the ground. I don't know for sure, but I'm guessing that he lied.
Retired and visiting as much of this beautiful country as I can.