Originally, Mirror Lake was a collection of bogs that were fed by an underground stream known as Neil Run. Formal development of Mirror Lake occurred in the 1890s when a philanthropist offered to build an observatory on campus if OSU would build beautiful landscape around it. This probably saved Mirror Lake from having a road built through it. At that time Mirror Lake developed a more formal and cohesive look. The water in Mirror Lake tasted so good that people drank from it at the turn of the 20th century. The university even built a grotto for people to visit and drink the spring water. Over time, the spring dried up from all of the construction on campus and along High Street. Olentangy River water was used until 1972 when it became City of Columbus water.
Mirror Lake has always been a place for student activities. One example was the Tug of War, between the freshmen and sophomore classes, which took place over Mirror Lake. Student organizations have used the Lake for ceremonies and hazing freshmen who did not wear their beanies (freshmen caps) or were found on the Long Walk of the Oval. In the late 1990s students began jumping into Mirror Lake before the football game against the University of Michigan (although students are strongly discouraged from going into the Lake).