Ivy League Group Agreement to all intercollegiate sports, effective with the 1955–56 basketball season. This is generally reckoned as the formal formation of the Ivy League. As part of the transition, Brown, the only Ivy that hadn't joined the EIBL, did so for the 1954–55 season. A year later, the Ivy League absorbed the EIBL. The Ivy League claims the EIBL's history as its own. Through the EIBL, it is the oldest basketball conference in Division I. As late as the 1960s many of the Ivy League universities' undergraduate programs remained open only to men, with Cornell the only one to have
Ivy League the NCAA tournament bid, then rebounded to win outright championships in 2012, 2013, and 2014. Harvard also won the 2013 Great Alaska Shootout, defeating TCU to become the only Ivy League school to win the now-defunct tournament. Rivalries exist between other Ivy league teams in other sports, including Cornell and Harvard in hockey, Harvard and Princeton in swimming, and Harvard and Penn in football (Penn and Harvard have won 28 Ivy League Football Championships since 1982, Penn-16; Harvard-12). During that time Penn has had 8 undefeated Ivy League Football Championships and Harvard has had 6 undefeated Ivy League Football Championships.