Prior to its 2010 cancellation, the Urban Ring Project planned for a circumferential BRT line with a stop at Mystic Mall.

Planning continued for the Chelsea segment; a Silver Line extension to Mystic Mall with a new commuter rail station was announced in 2013.

The Silver Line busway runs along the south side of the commuter rail tracks, crossing Everett Avenue at grade.

[4]: 336  On April 10, 1854, the Eastern Railroad opened a line from Revere to Boston, with trackage rights over the Grand Junction from Chelsea to Somerville.

[5] Streetcars and later automobiles cut heavily into the profitability of local commuter rail service; the B&M closed the station building in 1932, though some trains continued to stop.

[5] On December 27, 1966, an outbound Budd RDC struck an oil tanker truck at the 2nd Street grade crossing, killing 13 people.

[4]: 317  The residential neighborhood around 2nd Street, already planned for urban renewal, was destroyed by the Great Chelsea fire of 1973; it was replaced by industry and the Mystic Mall.

[18] Under draft plans released in 2008, a dedicated busway was to be built using the disused Grand Junction right-of-way, paralleling the active commuter rail tracks through Everett and Chelsea.

[16][4]: 337  Planning for some smaller corridors continued; the Chelsea–South Boston section was given high priority because Chelsea was densely populated yet underserved by transit.

The Silver Line alternatives terminated at the Chelsea commuter rail station or Bellingham Square and did not serve the Mystic Mall area.

[22] In March 2013, the MBTA began studying a possible extension of the Silver Line to Chelsea via a newly constructed bypass road in East Boston.

[23] In September 2013, the MBTA indicated that it would pursue the first alternative despite potential issues with bridge clearances and rebuilding Chelsea station.

[37] It opened on November 15, 2021, replacing the commuter rail platforms at Bellingham Square (which remains a Silver Line stop).