Operated by the New York, New Haven and Hartford Railroad (NH) from 1950, it took a route from Boston's South Station, running through southwestern Boston suburbs but making no stops until Blackstone, Massachusetts, then through northeast Connecticut along the path of the old Southbridge and Blackstone Railroad, divisions of the old New York and New England Railroad to Hartford's Union Station, and finally to Waterbury's Union Station.

Running directly through northeastern Connecticut, it made a shorter trip than the itineraries through Springfield, Massachusetts that the New Haven offered.

Even in earlier years, such as 1921, travelers continuing west on the same line beyond Waterbury, along territory of the former Central New England Railway, to Danbury, Brewster, Hopewell Junction, Poughkeepsie and Campbell Hall, New York in the mid-Hudson Valley, would need to transfer in Hartford or Waterbury for a Hartford - Campbell Hall train.

[6] The route was rendered unusable after a major flood during Hurricane Diane in August, 1955 washed out the bridge over the Quinebaug River, west of Putnam, Connecticut.

[7][8][9] With the closing of the route, Connecticut's interior cities no longer have east-west travel options available by rail.