Phi Sigma Kappa (ΦΣΚ), colloquially known as Phi Sig or PSK, is a men's social and academic fraternity with approximately 74 active chapters and provisional chapters in North America. Most of its first two dozen chapters were granted to schools in New England, New York, and Pennsylvania; therefore its early development was strongly Eastern in character, eventually operating chapters at six of the eight Ivy League schools as well as more egalitarian state schools. It later expanded to the South and West. The fraternity has initiated more than 180,000 members since 1873.