April 7th marks the celebration of when beer became legal again after President Franklin Roosevelt signed the Cullen-Harrison Act on March 23, 1933. That law became effective April 7th, which allowed beer to be sold in the United States after a 13 year hiatus. The only catch, the beer could not exceed 3.2% (4% ABV). Citizens stormed the businesses now able to sell beer like a Black Friday sale at WalMart.
The Great Experiment — From January 16, 1920 through 1933 beer suffered from prohibition (a ban on the sale, manufacture, and transportation of alcohol); although private ownership and consumption of alcohol was not outlawed. April 7th 1933, a full 8 months before the actual repeal of prohibition on December 5th, the beer started flowing again with FDR's repeal of the 18th amendment.
Happy Brew Years Eve — The Brewers Association at one point in time encouraged their members to celebrate National Beer Day, at that time it was known as Brew Years Eve and celebrated on April 6th, also going by the moniker New Beers Eve.
So, tell your friends about this glorious holiday, and raise a pint to remember this important event.