In 1966, the Boks moved back to the US, where Bart took up the roles of Head of the Department of Astronomy at the University of Arizona and Director of Steward Observatory, posts which he held until 1970. He was largely responsible for the construction of the telescope at the Kitt Peak National Observatory, and oversaw a doubling of the university's staff and growth in the graduate student program until by 1970 it was ranked fifth in the US, and Steward was regarded as "one of the world's premier astronomical research institutions."