Who Was Famous First Elvis Or Johnny Cash?

They actually both became famous at about the same time, though Elvis was a little ahead.

Cash was slightly older, being born in 1932. He formed his first band while in the US Air Force in the early 1950s, and started working for Sun Records in early 1955 with another band, the Tennessee Three. They were immediately successful, but national fame came in 1956 with "I Walk the Line" which stayed in the charts for 16 weeks and sold over 2 million copies.

Elvis Presley was born in 1935. He started working for Sun Records in 1954 - a year before Cash - and first came to national attention through radio shows and live tours. In 1955 there were already reports of rioting fans at his performances, and he was already nationally famous when he got his first number one single. This was "Heartbreak Hotel" in early 1956, and was followed by several other number one hits in the same year.

Cash performed first but Elvis made it big sooner that Johnny Cash.