Phi Kappa Psi (ΦΚΨ), commonly known as Phi Psi, is an American collegiate social fraternity that was founded by William Henry Letterman and Charles Page Thomas Moore in 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 179,000 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.