Tremont Street subway
The Tremont Street subway in Boston's MBTA subway system is the oldest subway tunnel in North America and the third-oldest still in use worldwide to exclusively use electric traction (after the City and South London Railway in 1890, and the Budapest Metro's Line 1 in 1896), opening on September 1, 1897. It was originally built, under the supervision of Howard A. Carson as chief engineer, to get streetcar lines off the traffic-clogged streets, instead of as a true rapid transit line.