If you go to the very far north west of campus...just north of Bates, there is the Alumni House. This is currently where the alumni office is located, but the door is open so you can go in. The first room on the right has all of the yearbooks back to like the 30s I believe. Really cool to look at!
There are also large photos on the walls in Gilmour Hall (second floor) showing campus aerial views over time.
I've never checked the libraries but I feel like they will also have old yearbooks as well, which may be an easier option.