The inaugural tournament, in 1939, had just eight teams, and saw Oregon beat Ohio State 46-33 for the title.
Since then, the tournament’s format has changed drastically.
In 1951, the field doubled to 16, and kept expanding sporadically over the next few decades until 1985, when the modern format of a 64-team tournament began.
In 1999, the Mountain West Conference joined Division I. In its second season, 2000-01, the conference received an automatic bid to the NCAA tournament, pushing the number of automatic qualifiers to 31, and the total teams in the tournament to 65. To account for this, rather than remove an at-large bid, the NCAA added a single game prior to the first round. This Opening Round game would pit the two lowest-seeded teams against each other to cull the field to 64 for the first round.
In 2011, to flesh out that first set of games and deepen the field, three more at-large bids were added, and with them, three more games to round out the First Four. That brought us to the current number of 68 teams.
So, who plays in the First Four?
When selecting the teams for the NCAA tournament, the Selection Committee ranks every team from No. 1 through No. 68. In its current format, the First Four consists of eight teams — the four lowest-seeded automatic qualifiers, and the four lowest-seeded at-large teams. Each subset plays against itself (i.e., at-large teams face at-large teams, and automatic qualifiers face automatic qualifiers).
Every year, the First Four is played on the Tuesday and Wednesday after Selection Sunday, with the Round of 64 starting that Thursday. The First Four has always been hosted at the University of Dayton. Here is more on Dayton’s impressive history as a college basketball town.
The First Four can often be found at the top of a bracket.
Here’s how this year’s bracket looks (and here’s a PDF):