Armitage opened on June 9, 1900 as a local station on the original Northwestern Elevated Railroad route from Lake and Wells in downtown to Wilson Station. An interlocking tower was added on the western platform following the construction of the State Street subway. From the late 1940s, Armitage became a station on the Ravenswood route (now the Brown Line). Purple Line express trains began stopping at the station in 1998 as part of an effort to help alleviate congestion on the Brown Line.
Armitage was renovated as part of the Brown Line Capacity Expansion Project. Many historic elements, including the station house, were preserved and renovated; the platforms were extended to enable eight-car trains; and elevators added to meet ADA accessibility requirements. The renovated station re-opened on June 5, 2008.