The Man in Black performed "I Walk the Line" the night he met his future wife.

Johnny Cash performs onstage with an acoustic guitar in a Sun Records publicity shot in 1957.

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July 1956 proved consequential for Johnny Cash. That July 7, he made his Grand Ole Opry debut, performing “I Walk the Line” at Nashville’s Ryman Auditorium, where he met future wife and duet partner June Carter. Two weeks later, on July 21, the song stepped to the top spot on Billboard’s country juke box chart (Most Played C&W in Juke Boxes), becoming the first of his 14 total No. 1s across three decades.

“Walk” was a bit quirky, built with five verses and no chorus wile wandering through three different keys. Those keys allowed the Man in Black to show off his vocal range, particularly the rumbling bass notes that became a signature.