Some things have gotten better on the T

The immediate cause of the accident appears to be that the wagon's wheel got stuck in the rail -- a complaint that we still hear about along surface streetcar routes. That would not, however, explain the pile of debris in the foreground, which appears to be from a different cause, perhaps some nearby construction.

It can't be on Main St. in Charlestown because there are no elevated tracks in the photo.

Bunker Hill St. in Charlestown is consistent not only with the destination sign on the trolley on the right, but also with the large signs advertising "Fare Five Cents - No Transfers". The two trolley routes in Charlestown (Bunker Hill and Main Sts.) were the only places where such a fare was collected in 1920.

I've travelled up and down Bunker Hill St. on Google Street View and I can't identify the location. Of course, a lot of buildings have been demolished since 1920, especially for the large housing project but also for later urban renewal pockets.

I think it may actually have been on Chelsea St. between City Square and the Navy Yard, which was traversed both by Bunker Hill St. trolleys and by Boston-bound trolleys of the Eastern Mass. St. Ry., coming from Chelsea, Revere, and Lynn. (That would explain the destination sign on the other trolley, which reads simply "Lynn".) This area along Chelsea St. has been completely changed twice, first for the Mystic River Bridge (Tobin Bridge) in the late 1940s, and again in the 1980s-90s.

If that's the case, then, this accident is tying up not only the trolley line, but THE major highway into Boston from the North Shore.

If they only had a Police Detail this would have never happened

Do you think those horses are still alive?

It doesn't say "Lynn" anywhere on the second trolley, at least not visible in the photo. However, another commenter ("anon") has identified the style of the trolley as belonging to the Bay State Street Railway, known by 1920 as the Eastern Massachusetts Street Railway. The destination sign "Boston" is also consistent with the Eastern Mass. St. Ry., which was by this time the only operator of trolley cars in the Boston city limits, other than the Boston Elevated Railway Company itself. (Boston Elevated trolleys would have had a destination sign that identified a specific destination, while signs on Eastern Mass. trolleys would have just said "Boston".)

The Eastern Mass. ran its trolleys over the Chelsea Bridge (basically a low-level drawbridge on the site of the present Tobin Bridge) and into Charlestown via Chelsea Street. From City Square in Charlestown, the Eastern Mass. cars crossed the river either on the Warren Bridge (now gone, on the site of the current dam) or on the Charlestown Bridge (still extant). The Eastern Mass. trolleys entered the subway at North Station but only went as far as the inner loop at Scollay Square ("Brattle Loop"); there they looped and went back to Charlestown, Chelsea, and beyond.

The Boston Elevated Railway trolleys serving Charlestown (today's #92 and #93 bus routes) followed the same route from City Square to the Brattle Loop / Scollay Square subway station, then looping back to Charlestown. The "no transfer" signs referred to the fact that the trolley riders would have to pay an extra fare to connect to other subway lines, or to take another streetcar. In 1920, most streetcars charged a 10-cent fare but you got a free transfer to the subway or to another streetcar -- indeed, to as many Boston Elevated Railway vehicles as you needed to complete your trip. The Charlestown streetcars were an exception at 5 cents with no transfer. (I believe you did have an option to pay 10 cents if you wanted to get a transfer.)

The Eastern Mass. operated many routes into Chelsea and then into Boston. Their streetcars originated in Salem, Lynn, various parts of Revere, Woodlawn in Chelsea, and parts of Malden. All these routes funneled onto Broadway at Bellingham Square in Chelsea, then over the Chelsea Bridge into Charlestown. From this picture it's not possible to tell which of these routes this particular trolley was serving, unless someone more expert than me can identify the particular type of streetcar and knows which route that type of car was assigned to. The Chelsea Bridge was the ONLY route used by the Eastern Mass. trolleys to enter Boston. It was also the primary route for vehicular traffic to enter Boston from points north. (Remember, the tunnels under the harbor didn't exist yet; there were ferries from East Boston into the North End.) There were also steam railroads serving the North Shore -- both the Boston & Maine, and the Boston, Revere Beach & Lynn (which connected with a ferry from Rowes Wharf to East Boston).

The horses are still alive and uninjured as of the time of the photo. It was the vehicle that was damaged, not the horses. They are standing there calmly awaiting further instructions. I doubt that the horses are still alive as of today.

Looking at detailed maps from 1912 and 1922, as posted on the "Boston Atlas" website [http://www.mapjunction.com/bra/], I've been able to identify the building in the center as number 95-97 Chelsea Street, at the corner of an alley called Mount Vernon Place. The trees to the left of that building are on the Navy Yard property, near the Commandant's House. All of the buildings visible in this photo were demolished in the 1940s to make way for the Tobin Bridge.

Does that answer everyone's questions?

In my earlier comment I wrote in error, "That would explain the destination sign on the other trolley, which reads simply 'Lynn'."

It should have read, "That would explain the destination sign on the other trolley, which reads simply 'BOSTON'."