As there is no connection between the inbound and outbound platforms, travelers must exit the station, cross the street, and pay again to switch directions at this station. Alternatively, a free inbound-outbound transfer can be made by traveling one stop east to Arlington station, where the two platforms are connected by a free mezzanine crossover.
Immediately west of Copley station, the Green Line "E" Branch splits off from the main line via a flat junction, and then runs under Huntington Avenue towards its terminus at Heath Street. Because inbound and outbound trains must be carefully coordinated when traversing the junction, this location is one of the bottlenecks limiting peak capacity of the Green Line.
Copley Station was opened October 3, 1914, as part of the Boylston Street Subway, an extension of the original Tremont Street Subway. The ornate wrought-iron head house next to the Boston Public Library was designed by the firm Fox, Jenny & Gale. Originally Copley had light blue and white tile mosaic for the station name on the walls; however, none of these have survived.
Substantial renovations were done in 2008-9 which included improving accessibility, new tiling, improved lighting and replacement of the two head houses on Dartmouth Street as well as restoration of the wrought iron head house next to the Public Library. The station remains one of the few in the MBTA system that do not have a crossover between outbound and inbound platforms.