Cost increases triggered a wholesale reevaluation of the GLX project in 2015, and a scaled-down station design was released in 2016.

A secondary accessible entrance from Boston Avenue also connects to the southeast end, with a grade crossing of the inbound Green Line track.

The Ball Square Traction Power Substation is located next to the northwest end of the station along Boston Avenue.

[10] A southbound freight train derailed at the station on June 25, 1916, blocking the line for over 24 hours and attracting 10,000 onlookers.

On April 18, 1958, the Public Utilities Commission approved a vast set of cuts to B&M commuter service, including the closure of North Somerville, Tufts College, and Medford Hillside stations.

[25][19] The Boston Elevated Railway (BERy) opened Lechmere station in 1922 as a terminal for streetcar service in the Tremont Street subway.

[28][29] In 1945, a preliminary report from the state Coolidge Commission recommended nine suburban rapid transit extensions – most similar to the 1926 plan – along existing railroad lines.

[34] The 1966 Program for Mass Transportation, the MBTA's first long-range plan, listed a short extension from Lechmere to Washington Street as an immediate priority, with a second phase reaching to Mystic Valley Parkway (Route 16) or West Medford.

[28][36] In 1980, the MBTA began a study of the "Green Line Northwest Corridor" (from Haymarket to Medford), with extension past Lechmere one of its three topic areas.

[37]: 308 [38] A 1991 agreement between the state and the Conservation Law Foundation, which settled a lawsuit over auto emissions from the Big Dig, committed to the construction of a "Green Line Extension To Ball Square/Tufts University".

The EENF identified a Green Line extension with Medford and Union Square branches as the preferred alternative.

[46] The Draft Environmental Impact Report (DEIR), released in October 2009, concurred with the Broadway site, noting also the connections available to the route 80 and 89 buses.

[49] Updated plans shown in June 2011 changed the headhouse exterior and modified the emergency exit from the northwest end of the platform.

[50] Plans presented in February 2012 added a bike cage, a traction power substation, and a drop-off area for The Ride at the lower plaza.

[51][52] By late 2012, the portion of the Medford Branch from Gilman Square station to College Avenue was expected to be completed by June 2019.

[53] A further update in June 2013 moved the headhouse back 60 feet (18 m) from Broadway to avoid a buried NStar power distribution line that had not been previously known.

The substation was set back from Boston Avenue to leave room for future transit oriented development, while part of the plaza became sloped terraces.

[54][55] Design was then paused while Phase 2/2A stations (Lechmere, Union Square, and East Somerville) were prioritized, as they were scheduled to open sooner than the rest of the GLX.

[58] At that time, cancellation of the project was considered possible, as were elimination of the Union Square Branch and other cost reduction measures.

Ball Square station was reduced to a single entrance from Boston Avenue with an at-grade crossing of the inbound track; there would be no elevators and no access from the Broadway bridge.

Several options to shorten the detour for pedestrians, including retrofitting the utility bridge to serve as a footbridge, were found to be infeasible.

[74][75][76] Several older buildings, including a bowling alley, were demolished in April 2019 to make way for the station and the traction power substation.