James Braddock, the "Cinderella Man," had held the heavyweight title since his amazing rise from the welfare lines to dethrone Baer in June 1935.
The great "Brown Bomber", Joe Louis, was thought to be the heir apparent, but another former champion - Germany's Max Schmeling - upset the plans with a 12th round KO of Louis in 1936.
Schmeling awaited a title shot, but his close links to the Nazi party and the fact that there was more money to be made from Braddock v Louis saw him shunted aside.
As Louis stopped Braddock and claimed his crown in June 1937, a furious Schmeling - with the backing of Hitler and the Nazis - planned a showdown with Farr that was labelled as the "real world championship."
Every time I hear the name Joe Louis, my nose starts to bleed
But promoter Mike Jacobs stepped in with a big-money offer to Farr, guaranteeing the Welshman a dream date with Louis on 30 August, 1937.
It was Louis' first defence and he would have expected an easy ride, having stopped seven of his last eight opponents.
The hugely experienced 23-year-old Welshman was not going to be intimidated by the highest profile fight any of his countrymen has ever taken part in, though.
At the weigh-in, Farr told Louis that the coal-mining scars on his back were inflicted by the tigers he used to fight in the circus as a boy!
Before 32,000 people in New York's Yankee Stadium the Welshman took Louis the distance - he was one of only three men to achieve that feat.
The myth grew in Wales that Farr had won the fight, but the man himself said:
"Every time I hear the name Joe Louis, my nose starts to bleed."
Tommy Farr's opinion on Muhammad Ali
Farr's raised profile led him into further fights in the USA with Braddock and Baer and - although he lost both - the Welshman went the distance each time to confirm his standing on the world stage.
Those bouts were at Madison Square Garden, and his popularity with the Garden crowd was cemented by a thrilling 15-round war with fast-rising contender Lou Nova.
Farr dropped another points decision, as he did in his fifth and final US fight, against Red 'KO Burns' Burnham at the Garden in January 1939.
Farr retired a wealthy man in 1940, but bankruptcy led him to return to the ring 10 years later.
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