Private operators The
Naugatuck Railroad began construction north from the
New York and New Haven Railroad (NY&NH) at Naugatuck Junction (Devon) in
Milford in April 1848. It opened in phases in 1849: to
Seymour in May, to
Waterbury in June, and to
Winsted in September. Service operated between Naugatuck Junction and
Bridgeport via
trackage rights on the NY&NH; Bridgeport has remained the southern terminal of service on the branch since. The
New York, New Haven and Hartford Railroad, successor of the NY&NH, leased the Naugatuck Railroad in 1887. The New Haven relocated the portion through Derby in 1903–1904, partially using the alignment of the
New Haven and Derby Railroad. The New Haven ended passenger service north of Waterbury in 1958; the line was abandoned entirely north of
Torrington in 1963. The New Haven merged into
Penn Central in 1969; Penn Central became
Conrail in 1976. Service was down to four daily round trips in the 1970s. The publicly-funded
Metro-North Railroad took over remaining commuter operations in the state, including the Waterbury Branch, in 1983. Metro-North increased service to six daily round trips in the 1990s. A new
Naugatuck Railroad associated with the
Railroad Museum of New England began operating excursion service north of Waterbury. The upgrades were to include a new signal system with multiple passing sidings to increase service – as it was the last remaining
dark territory of the Metro-North system – along with newer equipment and station rehabilitation. Signalization enabled multiple trains to safely operate on the branch at a time, while allowing for increased capacity and overall safer train operation. New
passing sidings were constructed at Derby and Beacon Falls, while existing sidings at Devon and Waterbury were upgraded, allowing trains to pass each other in single-track territory and thereby increase service frequency.
Centralized Traffic Control was activated on November 7, 2021. In 2022, the
Connecticut Department of Transportation studied the feasibility of electrifying the Waterbury Branch. Major damage from catastrophic flooding washed out the line in several locations on August 18, 2024. All service was suspended in favor of
replacement bus service while repairs took place. Service was restored on October 28, 2024. Prior to the 2020s, Waterbury was the only
accessible station on the branch. In November 2021, Governor Ned Lamont indicated plans to reconstruct the five non-accessible Waterbury Branch stations. By November 2024, the state planned to add accessible high-level platforms from 2025 to 2027. Groundbreaking for a relocated Naugatuck station took place in July 2025, with completion expected in mid-2027. Replacement of the existing Waterbury platform with a longer platform, along with the addition of a waiting room in the historic station building, began in October 2025 with completion expected in 2028. Construction on the remaining four stations began in May 2026 with completion expected in 2028. Buses will replace rail service from July 20, 2026, to May 31, 2027, to allow construction to take place. ==Stations==