Arizona State College at Flagstaff opened College Auditorium with the rest of the North Union in 1952. The 950-seat theater served as an assembly hall and presentation space for the growing campus. When the College became Northern Arizona University in 1966, it changed the name to University Auditorium. In 1985, the University renamed the hall to honor Robert Prochnow, an alum, veteran, and state senator who worked to save the college from closing after accreditation problems in the 1950s.
A number of visiting musicians, actors, speakers, and comedians have performed in the auditorium throughout the years. Notable acts have included the Kingston Trio and Dionne Warwick. In addition to holding ceremonial events and assemblies, in the 1980s the University began screening films here. Although other auditoriums have been built, Prochnow continues to host popular free movie nights as well as visiting artists and performers.