How ballsy were the Rolling Stones? Consider this: Without a real hit to their name in America, they walked into the home of their heroes and, with some of them in attendance, knocked ‘em flat. The result, an EP called 5 x 5, was released in the U.K. on Aug. 14, 1964.

The Stones made this special stop two months earlier while on their first U.S. tour. "2120 South Michigan Avenue was hallowed ground — the headquarters of Chess Records in Chicago,” Keith Richards wrote in Life. “We got there on a last-minute arrangement made by Andrew Loog Oldham, at a moment when the first half of our first U.S. tour seemed like a semi-disaster.”

A few days earlier in San Antonio, the band was actually booed offstage during uts set at the Teen Fair of Texas. At the time, they had only placed one song – a cover of Buddy Holly’s "Not Fade Away" – in the Billboard Hot 100, peaking at No. 48. (Their second U.S. single, the better-performing "Tell Me," would be released during the tour.) Walking into Chess proved to be the tonic the Rolling Stones needed, even if they were shocked by what they saw upon their arrival.

Reports vary as to what actually happened, but Richards has often stated that Muddy Waters was painting the ceiling. "Whether he was being a nice guy or he wasn’t selling records then,” Richards added. “I know what the Chess brothers were bloody well like: If you want to stay on the payroll, get to work.”

Others have said that Waters helped them unload their equipment. Regardless, it was still a shock for them to see that Waters, whose song "Rollin’ Stone" was responsible for the band’s name, being treated so poorly. On the positive side, he welcomed the young Brits with open arms.

“Actually meeting your heroes, your idols,” Richards continued. “The weirdest thing is that most of them are so humble, and very encouraging. ‘Play that lick again,’ and you realize you’re sitting with Muddy Waters. And, of course, later I got to know him.”

Listen to the Rolling Stones' 'If You Need Me'

The band cut about a dozen songs over a few days at Chess. Waters – and possibly Buddy Guy and Willie Dixon – watched them in the long, narrow studio on the second floor, impressed with what these young, scruffy, white Brits were doing with their music. Five of the songs wound up on 5 x 5.

Two of the tracks were their own compositions: Named after the address where it was recorded, "2120 South Michigan Avenue" was an organ-fueled instrumental that, oddly enough, owed more to Stax’s Booker T. and the MGs than the snarling Chicago blues. "Empty Heart" showed that they were still grappling with the idea of songwriting.

Both songs were credited to “Nanker Phelge,” a pseudonym the Rolling Stones used in the early days on songs written by all of its members, including “sixth Stone” Ian Stewart. “Nanker” referred to a silly face that the band – mostly Brian Jones – would make, while “Phelge” was the last name of a man who shared the flat in Edith Grove with Jones, Richards and Mick Jagger.

Of the covers, "If You Need Me" is a strong take on the Solomon Burke hit that was co-written by Wilson Pickett, and "Confessin’ the Blues" was a slowed-down version of Jay McShann’s swing-era hit. But the best track on the EP closed it out. Originally an unspectacular b-side to Chuck Berry’s "Johnny B. Goode," the Stones took "Around and Around," sped it up and knocked it out of the park.

The Rolling Stones added seven songs to the EP in October, including the hits "It’s All Over Now" and "Time Is on My Side," then released it in the U.S. as 12 x 5. The expanded album reached No. 3 on the Billboard 200.