The Shore Line, today's Northeast Corridor, was completed in 1858, but the Springfield route continued to carry most traffic until the bridge over the Thames River at New London, Connecticut, opened in 1889.

[4][5][6] By the startup of Amtrak on May 1, 1971, the Inland Route was no longer in use, but frequent Penn Central trains continued to serve the New Haven–Springfield Line.

[citation needed] Amtrak continued the Connecticut Yankee (by that time shortened to Philadelphia-Springfield) along the route.

With the November 14, 1971 timetable, this was assigned the name Bay State, and extended south from Philadelphia to Washington, DC.

The train was discontinued March 1, 1975, though on October 31 of that year, the Boston section of the Lake Shore Limited began, restoring Springfield–Boston service.

[7] On April 1, 1976, Amtrak acquired the New Haven–Springfield Line from the newly formed Conrail, along with most of the Northeast Corridor.

[16] Amtrak runs Hartford Line trains between Springfield, Massachusetts, and New Haven, Connecticut.

The study culminated in a final report in 2005, which was presented for a grant application to the Federal Transit Administration New Starts program.

Stations at Wallingford, Meriden, and Berlin were completely rebuilt, while New Haven State Street and Hartford had improvements made.

[22] Expanded Amtrak Shuttle service on the line launched one week earlier on June 9, 2018.

[23] Connecticut DOT provides eight round trip commuter trains on weekdays under its CT Rail branding that are operated by its new contractor, a joint venture between TransitAmerica Services and Alternate Concepts Inc.[24] Half of these trains operate between New Haven and Hartford, with the other four running the whole line between New Haven and Springfield.