Show an empty tournament bracket to a random sample of Americans and they're likely to make the same instant association: NCAA basketball.
This simple design, which is used whenever a competition needs to winnow a large group of contestants to a single winner, has become a much-admired cultural meme. If there were a hall of fame for sports graphics, the bracket would be the first inductee.
But as ubiquitous as brackets have become, they're also the center of a surprising mystery: Nobody knows for sure where the idea came from.
College basketball's National Invitation and NCAA basketball tournaments began in 1938 and 1939, respectively, and soon after, brackets began to appear in some newspapers. The NCAA says the first complete bracket in its basketball archives is from 1943.