Extensions opened to Waterbury June 11 and the rest of the way to Winsted September 24, where the Central New England Railway later passed through.

The Thomaston Dam flood control project constructed by the Army Corps of Engineers required roughly 8 miles (13 km) of track to be relocated between 1959 and 1960.

On January 1, 1971, the State of Connecticut and the MTA leased passenger and freight operations along the Waterbury Branch to Penn Central.

Freight traffic continued to decline through the 1970s as many of the factories along the line that shipped by rail closed and relocated out of the region.

While railroads museums would later be established at those sites, RMNE continued its search for a rail line they could operate their own excursions.

When Boston & Maine ended operations on the Torrington Secondary, ConnDOT made the line available to RMNE's Naugatuck Railroad subsidiary.

While NAUG's operating limit begins nearby Metro-North Railroad's Waterbury station, no coordinated connecting passenger service is available.