The East Boston Tunnel was opened to Boston Elevated Railway (BERy) streetcar service as far as Court Street on December 30, 1904.
Court Street proved to be a problematic terminus; its stub-end single-track design limited frequent service and resulted in several fatal crashes.
The Boston Transit Commission (BTC) began construction of a 0.5-mile (0.8 km) extension of the East Boston Tunnel on November 29, 1912.
The extension ran from Scollay Square (where a new platform was constructed to replace Court Street station) to a new station and loop at Bowdoin Square.
Tracks continued west under Cambridge Street to an incline at Joy Street, where streetcars could continue on surface tracks to Charles Street and the Longfellow Bridge to Cambridge.

Bowdoin was built with a wedge-shaped island platform inside a balloon loop, which eliminated the awkward end-changing required at Court Street and allowed use of unpowered trailer cars in the tunnel to increase capacity.
The station had two staircase entrances at the west end of Bowdoin Square, adjacent to the Parkman building.
The finish of Bowdoin and Scollay Under stations was similar to Washington station (opened 1915) and the Boylston Street subway stations (1914): granolithic platforms, wainscotting of white polished terrazzo, and white plaster upper walls and ceiling.
Bands of ceramic tile trimmed the wainscotting; at Bowdoin, the tile was dark blue.
The stairwells were walled with polished Quincy granite and roofed with smoothed concrete.

Construction of the station began on March 2, 1914; 247 men were employed for the work.
Several buildings had to be underpinned to allow the loop to be built underneath them.
Construction of the station was completed on December 4, 1914, with finish work following.
The extension opened on March 18, 1916.
All streetcar lines from East Boston looped at Bowdoin except for a Central Square, Cambridge–Orient Heights line.
The East Boston Tunnel was opened to Boston Elevated Railway (BERy) streetcar service as far as Court Street on December 30, 1904. Court Street proved to be a problematic terminus; its stub-end single-track design limited frequent service and resulted in several fatal crashes. The Boston Transit Commission (BTC) began construction of a 0.5-mile (0.8 km) extension of the East Boston Tunnel on November 29, 1912. The extension ran from Scollay Square (where a new platform was constructed to replace Court Street station) to a new station and loop at Bowdoin Square. Tracks continued west under Cambridge Street to an incline at Joy Street, where streetcars could continue on surface tracks to Charles Street and the Longfellow Bridge to Cambridge.
Bowdoin was built with a wedge-shaped island platform inside a balloon loop, which eliminated the awkward end-changing required at Court Street and allowed use of unpowered trailer cars in the tunnel to increase capacity. The station had two staircase entrances at the west end of Bowdoin Square, adjacent to the Parkman building. The finish of Bowdoin and Scollay Under stations was similar to Washington station (opened 1915) and the Boylston Street subway stations (1914): granolithic platforms, wainscotting of white polished terrazzo, and white plaster upper walls and ceiling. Bands of ceramic tile trimmed the wainscotting; at Bowdoin, the tile was dark blue. The stairwells were walled with polished Quincy granite and roofed with smoothed concrete.
Construction of the station began on March 2, 1914; 247 men were employed for the work. Several buildings had to be underpinned to allow the loop to be built underneath them. Construction of the station was completed on December 4, 1914, with finish work following. The extension opened on March 18, 1916. All streetcar lines from East Boston looped at Bowdoin except for a Central Square, Cambridge–Orient Heights line.
Bowdoin station