Phi Kappa Psi (ΦΚΨ, Phi Psi) is an American collegiate social fraternity founded in the southwest corner of the second floor of Widow Letterman's home on the campus of Jefferson College in Canonsburg, Pennsylvania on February 19, 1852. There are over 100 chapters and colonies at accredited four year colleges and universities throughout the United States. More than 119,000 men have been initiated into Phi Kappa Psi since its founding. Phi Kappa Psi and Phi Gamma Delta, both founded at the same college, form the Jefferson Duo.