Pi Beta Phi (ΠΒΦ) is an international Fraternity for Women, founded at Monmouth College, in Monmouth, Illinois on April 28, 1867 as I.C. Sorosis, the first national secret college society of women to be modeled after the men's Greek-letter fraternity. According to G. William Domhoff, in Who Rules America? (Seventh edition, p. 57), Pi Beta Phi was cited as one of the four or five sororities upper-class college women "joined with nationwide social prestige". Its headquarters are located in Town and Country, Missouri, and there are 200 chapters ever installed and more than 300 alumnae organizations across the United States and Canada. Once an initiated member in good standing graduates or otherwise leaves her college or university, she is a member for life.