Sigma Alpha Iota was founded at the University School of Music in Ann Arbor, Michigan on June 12, 1903, to "form chapters of music students and musicians who shall by their influence and their musical interest uphold the highest ideals of a music education; to raise the standard of productive musical work among the women students of colleges, conservatories and universities."  The fraternity was founded by seven outstanding women: Elizabeth A. Campbell, Frances Caspari, Minnie Davis Sherrill, Leila Farlin Laughlin, Nora Crane Hunt, Georgina Potts, and Mary Storrs Andersen.

As of Aug. 1, 2021, SAI has 133,245 initiated members, 210 active collegiate chapters, and 113 active alumnae chapters including the International Chapter.