One of his most famous songs, "I Walk The Line" details Johnny Cash's values and lifestyle. It was a promise to remain faithful to his first wife, Vivian Liberto, while he was on the road.

Cash was 22 when he married Vivian on August 7, 1954; their daughter Rosanne was born 10 months later.

Cash got a taste of temptation later in 1955 when he signed with Sun Records. He released two singles for the label that year and toured with their star, Elvis Presley, who attracted throngs of female fans at every stop.

Cash wrote "I Walk The Line" as a reminder to stay true, which it turned out was not very, very easy to do. When the song took off, he became a star and was suddenly enveloped in distractions and vice.

Constantly touring, Cash was rarely home.

In 1956 he met June Carter at the Grand Ole Opry; in the early '60s, they started working together and also kindled an affair.

Vivian filed for divorce in 1966; it was finalized a year later and, in 1968, Cash and Carter got married. That one took: they were together until June's death in 2003.