There are many stories about people who have travelled back and forth from Canada to the United States, to suddenly, one day, out of the blue, get caught for a long-forgotten record.
In one recent example, a journalist was travelling south with her mother. She had completely forgotten about a fine that she had received in the States 26 years earlier. The resulting incident was not what you would call pleasant.
Basically her story went like this:
She was on a flight to the U.S. a quarter of a century ago with an old boyfriend. Customs caught him with a tiny, stained pot pipe tucked into his shorts. Worried that he might go to jail because of his previous record, he asked his girlfriend (the journalist) to take the heat. She did. And wound up with a $75 fine and a boot back to Canada.
Either way, she completely forgot about the incident. There was no documentation or any kind of follow-up.
Needless to say, she went back and forth through the border several times without thinking twice about the incident. Until one day, they pulled her aside. And that day she just happened to be with her mother.
Her fine from 26 years ago came up (these incidences are never erased) and as a result, she had to be fingerprinted and photographed for the FBI's files. She was also deported. For good.
This journalist now joins the ranks of 40,000 Canadians that are rejected at the American border each year. The only way through is an Entry Waiver. About 4000 waivers are granted each year.
Instead of having your travel plans ruined as well, it is something you should look into first.