National Industrial Recovery Act, but two years later the Supreme Court declared it unconstitutional, and it was abolished. Not to be deterred, in 1938 FDR re-established a minimum wage of $0.25 per hour ($4.10 in 2012 dollars) as part of the Fair Labor Standards Act), and this time the Supreme Court upheld it, ruling that Congress had the power (under the Commerce Clause) to regulate employment conditions.
But the story behind it's birth is much more complicated than that, and it's the subject of a recent Planet Money podcast ("Birth of the Minimum Wage"). The folks at Planet Money are planning a follow-up podcast on the economics of the minimum wage. I'll post a link to that when it appears.