Knapp worked for a short time in the classics department at
Colby College and in the history department at the
University of Utah. After that, he went to the classics department at the University of California, Berkeley, in 1974. He remained there until his retirement in 2006, eventually attaining the rank of professor. Besides teaching and doing research, he served in numerous administrative posts including as chairman of the classics department and the Department of East Asian Languages and Cultures, as dean in the College of Letters and Science, and chairman of the Berkeley faculty Senate. ==Selected publications==