Pi Sigma Alpha was founded in 1920 at the University of Texas for the purpose of bringing together students and faculty interested in the study of government and politics. Professor C. Perry Patterson was an early leader of the first chapter and served as national president of PSA from 1920 until 1932. The success of the honor society at the University of Texas prompted other institutions to apply for chapters, with the Universities of Oklahoma and Kansas establishing chapters by 1922. In March of that year the society held its first national convention at the University of Oklahoma.
Growth in the honor society was gradual throughout the 'twenties and 'thirties and accelerated after the Second World War; today there are over 650 chapters throughout the country. There is at least one college or university with a Pi Sigma Alpha chapter in every state and the District of Columbia and, as of 1995, the U. S. territory of Guam.
Pi Sigma Alpha, the National Political Science Honor Society, is the only honor society for college and university students of government in the United States. The number of Pi Sigma Alpha chapters on campuses across the country is rapidly approaching 700. Pi Sigma Alpha is a member of the Association of College Honor Societies.