The Department of Astronomy was championed and established by Professor C.A. Chant. It began in 1905 as a Sub-Department of Astrophysics within the Department of Physics, was referred to briefly as the Astrophysics Department, and became a separate Department of Astronomy in 1920. The early 1930's were taken up with planning for the David Dunlap Observatory, whose telescope was the second-largest in the world when it opened on May 31, 1935. The Department operated the DDO until its closing in 2008. The Department expanded greatly in the 1960's, both in the range of research interests, and in the number of faculty, staff, graduate and undergraduate students. In 2001, after considerable internal debate, it became the Department of Astronomy and Astrophysics, to reflect the breadth of its research, teaching, public outreach, and other activities.