The Cambridge subway opened in 1912; planning for an infill station at Charles Street began in 1924. After several false starts, construction of Charles station began in 1931. The Art Deco station, with cast stone headhouse and copper-sheathed platforms, opened on February 27, 1932. A pedestrian tunnel that provided station access was replaced by footbridges in 1961. The station was renamed Charles/MGH in 1973. From 2003 to 2007, the station was renovated for accessibility; a new glass entrance replaced the original structure. The proposed Red–Blue connector would extend the Blue Line to Charles/MGH, with a new underground platform level.