The Orange Line as it now exists has been totally
transformed over its long history.
The route was long known as the Main Line Elevated, and more locally,
as the Charleston Elevated beyond North Station up to Everett, and
Washington St. Elevated south of downtown. The northern portion was replaced,
put on a new vector, and lengthened to Oak Grove
in the 1970s. The southern portion to Forest Hills
was rerouted in the early 1980s, marking an end to extended elevated
trackage on the Boston subway system.
The journey through center city started out in the earliest years of
last century with trains using the Tremont St. tunnel. That
route was shared with the city's underground streetcar service, but
each system had its own trackage.
Soon after, the construction of the Atlantic Ave. Elevated provided
an alternate route through downtown, closer to the Harbor. The Washington St. Tunnel
replaced the Tremont St. subway very early on; and the Atlantic Ave.
service lasted only until the late-1930s.
The above photo is on the northern portion of the current Orange Line on the way out to Oak