Robbie Robertson has repeated this story Levon Helm recounted in his autobiography, the Robertson telling of the story viewable on You Tube: In the Summer of ’65, The Hawks had a week off (they were a working band, playing on the circuit in the South, Midwest, and up and down the East Coast), so the four Canadians suggested they go to Levon’s hometown in Arkansas, Helena, to look up fellow Helenian Sonny Boy Williamson. Levon had gone down to the local radio station in the afternoon after high school got out for the day, watching and listening to Sonny Boy and his band perform live in the studio.
The Hawks found Sonny Boy walking down a street in Helena, and suggested they go somewhere to get a drink. He took them to the home of a woman who ran a booze & barbeque joint in her living room, where he and they spent a few hours getting drunk and playing music. Sonny Boy told them that he had just returned from a tour of the UK (where the Blues Revival was already in full bloom, a couple of years before it flowered in the U.S., though The Paul Butterfield Blues Band, with Mike Bloomfield on guitar, were already making their first Elektra album), and said the backing bands he had been provided with by the promoter (one of which was The Yardbirds, with a very young Eric Clapton on guitar) "wanted to play the Blues SO bad, and that’s just how they play it" ;-) .
SBW and The Hawks made tentative plans to hit the road together in the U.S., but he passed away before that could happened. Bob Dylan hired them later that year, and took The Hawks with him on his UK tour in the Fall. In the audience on that tour were The Beatles, The Stones, and all the other UK bands, getting shown what a really good (heh) band sounds like.