It would soon become one of Bruce Springsteen's defining moments but, at the time, the song didn’t even have its famous title: Springsteen and the E Street Band performed what would become "Thunder Road" live for the first time on Feb. 5, 1975.

The concert was a benefit for the Main Point, a small coffeehouse in Bryn Mawr, Pa., where Springsteen had played about 25 times since 1973, and broadcast over Philadelphia radio station WMMR. He had already written and recorded the song "Born to Run" the previous summer, but sessions for the album of the same name had yet to begin.

As such, Springsteen was going to use the show to try out some of his new songs, which, Brucebase notes, almost caused him to change his mind about the broadcast. Fortunately, WMMR DJ Ed Sciaky, who introduced Springsteen onstage that night, was able to talk him into it. The show is one the best and most famous concerts from Springsteen's early days, giving a fascinating glimpse at the work-in-progress.

At the time — or at least how it’s credited on numerous bootlegs — the song was called "Wings for Wheels." While the melody and escapist theme were in place, the song's arrangement and lyrics would get some fine-tuning by the time they entered the studio. The girl’s name would be changed from “Angelina” to the less-bulky “Mary," some verses would be entirely rewritten and the instrumental break at the end would take on a more stately tone.

Most of all, the song needed a better title, one that would prove more evocative. Introducing the song at a concert three years later, Springsteen noted that a 1958 Robert Mitchum movie about back-road bootleggers provided the inspiration for the track's new title. "I never saw the movie," Springsteen said. "I only saw the poster in the lobby of the theater."

Three other unreleased songs performed that night were also in embryonic stages. "Jungleland" would also undergo a similar rewrite — an unfocused guitar and violin duet would be replaced by Clarence Clemons’ iconic saxophone solo — and "She’s the One" still included lyrics that would eventually wind up in "Backstreets." And "A Love So Fine" was later renamed "So Young and in Love," finding a home on the 1998 outtakes boxed set, Tracks.

The rest of the concert – which, at 160 minutes, was one of his longest to date – reveal definitive performances of Springsteen's early material, including a piano-and-violin version of "Incident on 57th Street" that opened the show, a slowed-down "E Street Shuffle" with a fictionalized account of how he met Clemons and a raucous take on "It’s Hard to Be a Saint in the City." The band performed three covers: "Mountain of Love" (a Top 10 hit for Johnny Rivers in 1964), Bob Dylan’s "I Want You" and Chuck Berry’s "Back in the U.S.A.," which closed out the night.

But the most surprising aspect of the concert, particularly for those who collect Springsteen bootlegs, is hearing "Born to Run" show up as the third song in the set. By the end of 1976, the song found its way to the encore where, with few exceptions, it would remain.