John Austin Gronouski was born in Dunbar, Wisconsin, on October 26, 1919. Gronouski attended St. Peter's School in Oshkosh, Wisconsin, and then studied at Oshkosh Teachers College. He received a B.A. in 1942 from the University of Wisconsin.

Following graduation, Gronouski joined the Army Air Corps and served as a navigator with the Eighth Air Force. Gronouski was discharged in October 1945, returning to the University of Wisconsin to earn his M.A. in 1947; he then took various lecturing and research positions from 1948 to 1953. In 1955, Gronouski earned his Ph.

D. from the University of Wisconsin, and continued to teach and conduct research until 1959, when he was appointed research director of the Wisconsin Department of Taxation. Gronouski was also named executive director of the Revenue Survey Commission that same year. In 1960, he became Wisconsin state commissioner of taxation.

Gronouski took over the slot of postmaster general from J. Edward Day on September 30, 1963, and held that position into the Johnson administration, resigning on November 2, 1965. As postmaster general, Gronouski added the use of the zip code, instituted a vertically improved mail system of delivery, proposed to do away with airmail postage, and reclassified first class mail as a priority class.

After his time in the cabinet, Gronouski served the United States as ambassador to Poland, a post he held from 1965 to 1968. John A. Gronouski died on January 7, 1996.