One of the nation's oldest fraternities has voted to allow transgender men to pledge and become members.

Founded at Princeton University in 1824, Chi Phi changed its membership policy effective immediately in all 52 chapters nationwide.

"We felt this amendment to Chi Phi's Constitution would change the conversation surrounding transgender men and their ability to join the fraternity," said Sam Borchart, the undergraduate membership-committee chairman.

"One change is never a stopping point, and we hope this opens the door to further discussion about inclusivity, particularly for transgender men who want to join us in this fraternity."

Any male applicant will have to prove their gender with legal documentation, though it's not clear what that would entail.

The National Center for Transgender Equality's Mara Keisling praised the move, but was still concerned that the need for "documentation" would exclude many young trans men, who may be at different points in their transition.

Other nationwide Greek organizations have begun accepting trans members, though Chi Phi is one of the most prestigious. Members include former governors, senators, professional athletes and venerated broadcaster Walter Cronkite.

It's mission is "to build better men through lifelong friendships, leadership opportunities and character development."