Boston is home to one of the oldest subway systems in North America. The MBTA Blue Line opened in 1904 and originally used trolley cars rather than subway trains. Today, the blue line continues to operate between Bowdoin and Wonderland stations. Part of the line closer to Boston’s city center is a traditional underground subway with a third rail used to provide electricity while other portions of the line are above ground and use overhead catenary to supply power. To accommodate the two differen