If you look at a map of the MBTA’s Green Line, you’ll see lines marked B, C, D, and E.

But once upon a time, there was an “A” as well. The A-Line ran from Brighton to Watertown through Newton Corner. Its last trip was June 20, 1969. Today, the 57 Bus runs the same route.

The MBTA only introduced color lines in 1967, so technically the A-Line (named as such) only existed for two years; but the route, in various pieces, had existed for almost a century.

The beginnings of the A-Line were in the 1860s with the first horse-drawn railcars. It would not reach Newton until 1896, by which time horses had been replaced by electricity. The extension to Watertown opened in 1917. In 1941, it became the first line in Boston to have PCC cars—the iconic streetcar design—which later became used throughout the transit system.

Today, all local train service in the Boston metropolitan area is provided by the MBTA, with the only competing trains being interstate rail run by Amtrak. This was, however, very much not the case in the early years of rail service. There were dozens of small railroad companies, many of which only operated one line. Newton had many of these. The Newton Railroad Company began horsecar service between Union Square and Oak Square in 1858. Only a few years later, it merged with the Cambridge Railroad Company, which extended the line to Newton Corner but then cut it back to Oak Square again. It then changed hands again to be owned by the West End Street Railway, which expanded and electrified it.

Finally, the Boston Elevated Railway ran it and created its final route path. The Boston Elevated Railway would be taken over by the Metropolitan Transit Authority in 1947, the entity that later became the MBTA.

The A-Line was a streetcar, so it ran directly in the street. This was fine in the early years, when very few people had cars and there was immense demand by people from Newton, Watertown, and Brighton to reach downtown Boston for employment, shopping and leisure.

But by the 1950s, there were beginning to be issues. More people owned a car, meaning less demand for public transit, especially slow public transit like a streetcar. Streetcars were annoying for drivers. More people were also moving farther out from the city, taking advantage of not only cheaper cars but vastly improved highway networks. One of these was the Massachusetts Turnpike. Newton Corner had a new ramp over the new highway, which the A-Line ran on—against the flow of traffic, directly in the middle of the street.

While ridership was down in general, there was one place in the system where that wasn’t true: the newly opened D Line. While it used the same cars as the A Line, it ran on its own right of way, not in the street. The D Line replaced a heavy rail line run by the Boston and Albany Railroad.

The heavy rail line had had 16 daily trips and 3,140 passengers. In 1959, the D-Line had 134 daily trips and 26,000 passengers.

Running 134 daily trips takes a lot of train cars. While the MTA had purchased 17 additional PCCs from Dallas, having enough trains and being able to maintain them was a continual issue. It attempted to buy more trains from Toronto and Pittsburgh but was unsuccessful. In 1966, there were only 343 cars available, some of which were in poor condition.

New buses in Watertown reduced the demand for the A Line further. To be able to maintain service on the rest of the system, the A-Line was closed and replaced with a bus.

The community was not happy, but initially, it seemed like service might eventually be restored, especially as the T did later purchase new Green Line cars. The A-Line tracks remained as a way to get cars in need of repair to the Watertown car house. As the decades went by, fewer people wanted the return of the streetcar and more people were annoyed by the frustrating experience of driving on trolley tracks. Most of the tracks were removed in 1994, although some stub pieces of tracks remained visible until recently, and there are still some tracks at the car house itself.

The A-Line’s existence is almost completely gone, but not quite. There are six remaining functioning PCCs running every day on the Mattapan High Speed line in Boston.

The MBTA continually threatens to get rid of them, but as of right now, they’re still going. You can’t take the A-Line, but you could take a train that once ran on the A-Line. (And if for some reason you want to experience driving on trolley tracks, the E-Line south of Brigham Circle is still a streetcar).