The station was built with an auxiliary entrance at Circle Avenue that was eventually converted to a single turnstile facility.

A Roos chest-making factory (founded in 1871) was located west of the station and Circle Avenue until it was torn down in 2013 to make way for a new recreation park that opened there in 2018.

Harlem is open 24/7 365 days a year as part of the overnight service of the Blue Line and an annual total of 346,005 passengers have boarded the station in 2012.

The Aurora Elgin and Chicago Railway (AE&C) began service on August 25, 1902, and opened a station on Wisconsin Avenue by October.

The Garfield Park branch, opened by the Metropolitan West Side Elevated Railroad in 1895, abutted the AE&C's line and took over local service in the area on March 11, 1905.