1950's
In 1950, burdened by I.R.S. debt, he announced a comeback and was promptly given a chance to recover his title, but he lost a 15 round unanimous decision to world champion Ezzard Charles, who had won the title after Louis left it vacant. He kept boxing, and in his next fight he beat fringe contender Cesar Brion by a decision in 10. Seven more wins followed, including a rematch with Brion and a decision over fellow hall of famer Jimmy Bivins. In 1951, however, he would box what would be his final fight: In front of a national television audience, Louis lost by a knockout in eight rounds to the future world Heavyweight Champion, Rocky Marciano. Louis did not embarrass himself that night, but it was obvious his best years had gone by. He retired with a record of 68 wins and 3 losses, with 54 wins by a knockout.

Louis became a professional wrestler in 1956 but quit in 1957 due to injuries suffered during a match.

Louis faced a drug problem, a fact not too many people knew about but which was made public by a boxing book published by Ring Magazine, just as in Sugar Ray Robinson's case. But later on in life, he was able to kick his drug habit.

http://www.fameboxing.com/joe-louis.htm