The Charlestown Elevated closed on April 4, 1975, and the new segment from Haymarket to Sullivan opened on April 7. This segment was a direct replacement for the El: North Station and Sullivan replaced nearby elevated stations, while roughly replaced the former and stations. The next section, from Sullivan over the new Edward Dana Bridge to , opened on September 6, 1975. The Wellington Shops for railcar maintenance, which replaced the Sullivan Square Shops and later the Forest Hills Shops, were opened with this extension. An additional segment to the elevated , which includes a platform for the Haverhill Line, opened on December 27, 1975. The sixth and terminal station, , opened on March 20, 1977.