OOOHHHH! I REMEMBERED!
Phi Sigma Pi started because the Beta chapter of Phi Lambda Epsilon was closed. (I've googled that fraternity and I think the whole org is gone)
It began at the State Teacher's College at Warrensburg, Missouri as a Professional Honorary Fraternity in 1916. It eventually evolved into a Professional Education Fraternity for Male Teachers and in 1966 expanded as an honor fraternity that included all disciplines. We went co-ed in 1977.
I think it's funny that women were granted membership only thirty years ago and now we dominate most chapters.
*Also, it's not my org-but Delta Omicron is a music sorority and it admits men. I was flabbergasted when I learned that.