Oak Park station was opened on January 25, 1901, by the Lake Street Elevated Railroad as a surface-level station on the line that ran parallel to the former Chicago and Northwestern Railway line (today's Union Pacific / West Line). Both lines created an unsafe grade crossing, especially as the community moved from horse-powered vehicles to the automobile. When the C&NW elevated its line between 1908 and 1909, it created a blind spot for traffic trying to cross the Lake Street Line.
On October 28, 1962, the station was elevated on an embankment and the main entrance was rebuilt by taking advantage of the small space along the road to include a ticket window and enclosed waiting rooms. When the Green Line was closed for a renovation project in 1994, the CTA had planned to permanently close the Oak Park station along with four other stations (Austin, Laramie, Homan and Halsted). However, due to the political pressure and complaints of residents, the station was retained without being rebuilt and reopened with the Green Line on May 12, 1996. When it reopened, the committee of disabled residents of Oak Park strongly protested it as one of the few stations of the Green Line that is inaccessible to persons with disabilities.