Mike Andriatch asked about this topic, which has come up before. Up to the mid-60s there were a relative handful of departments, some very broad, e.g. "Science." Then in '66-67 the school as part of its expansion offered more and more electives and majors, and the bigger department groups were broken out into their constituent parts, Dance, Geology etc.
Based on some initial research, including an organization chart from '66 I sent Mike, I suggested that next year, 2017, would historically be appropriate to celebrate, or begin celebrating, 50 years as a comprehensive liberal arts college.