Tonks was Professor of Art History Emeritus at Vassar College.
[1] He was the first to be awarded a doctorate at Harvard in that field, and wrote a dissertation on the Brygos Painter.
[2] Additionally, Tonks was a fellow at the American School of Classical Studies at Athens for the 1901 to 1902 academic year.
From 1905 to 1911, Tonks was hired by Allan Marquand to teach art history and archeology at Princeton University.
In that final year, he was hired as Chair and Professor of Art History at Vassar College until his retirement in 1944.