One hailed from Minnesota, the other from Arkansas. Both appeared on the bill at the 1964 Newport Folk Festival. During a hotel-room jam, Johnny Cash presented Bob Dylan with a treasured Martin guitar — a symbol of respect and admiration — and their friendship was secured.
Dylan admired Cash's recordings for Sun Records in the 1950s. Cash became a fan of Dylan's 1963 release, The Freewheelin' Bob Dylan, playing the record incessantly. A correspondence ensued.
At Newport, Cash included "Don't Think Twice, It's All Right," a Dylan song, in his set. Dylan called the moment "the high thrill of a lifetime." Just a few months later Columbia released Cash's recording, with June Carter, of Dylan's "It Ain't Me, Babe," and the record became a hit. As Dylan shifted away from the protest songs that first attracted attention, Cash defended his friend's new creative direction.
While Dylan was recording Nashville Skyline in February 1969, Cash dropped by, and over the course of two days they recorded numerous duets. Their performance of Dylan's "Girl from the North Country" appeared on Nashville Skyline, and Cash wrote Grammy-winning liner notes for the album. Dylan wrote "Wanted Man" for Cash, and Cash debuted the tune when he entertained the inmates at San Quentin prison.
(Source: CountryMusicHallofFame.com)