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Cos Cob Power Plant Records

Identifier: 1988-0024

Scope and Content

The records consist of blueprints and wiring diagrams for the electrical systems of the electrified railroad zone of Woodlawn, New York, to Cedar Hill in New Haven, Connecticut, that provided power to the New York, New Haven & Hartford Railroad, generated by the Cos Cob Power Plant. The records also include architectural drawings, foremen's log books, records of coal received, and administrative correspondence concerning the power plant and the Mianus River Dam.


  • undated, 1891-1986


The collection is open and available for research.

Restrictions on Use

Permission to publish from these Papers must be obtained in writing from the owner(s) of the copyright.


The Cos Cob Power Plant was conceived in 1903 as a result of the New York State legislature’s law that prohibited all steam locomotives from entering New York City after 1908 due to train wrecks in the Park Avenue Tunnel caused by low visibility from locomotive smoke and steam. The New York Central Railroad, which operated all railroad traffic between Woodlawn, New York, into New York City, decided to install a low-voltage direct current third-rail electrical system; thus after 1908 all locomotives coming into New York City's Grand Central Terminal (then under construction), would be forced to operate off third- rail.

Although the New York, New Haven & Hartford Railroad, better known as the New Haven Railroad, operated considerable low- voltage direct current trackage at this time, this system was considered inadequate for the operation of heavy trains over long distances at high speeds. The New Haven Railroad’s engineers, working with Westinghouse Electric and Manufacturing Company of Pennsylvania, decided to install high-voltage 11,000 volt overhead wires on the tracks from Woodlawn, New York, into Connecticut. These wires would be powered from the railroad's own power station, using single-phase alternating current (ac) electricity. This was done at a time when low-voltage direct current electrification was the rail standard of the day.

Construction of the power plant began in 1905 in Cos Cob, Connecticut, located in the town of Greenwich on the Mianus River. On 24 July 1907, the first New Haven Railroad electrified passenger train traveled from Grand Central Terminal to New Rochelle, New York. The initial electrification covered all four tracks to Stamford, Connecticut, and in 1913-1914 was extended to New Haven, Connecticut.

The New York Central Railroad's third-rail system from Woodlawn, New York, into Grand Central Terminal required the New Haven Railroad's locomotives to operate both off this system and on their own high-voltage overhead wire. This meant that these locomotives and multiple unit cars had to change over between these two systems while moving at track speed. With so much traffic it was considered unworkable to stop every train for the changeover.

The initial overhead catenary construction from Woodlawn to Stamford utilized two parallel messenger wires supporting a single trolley wire by vertical hangers, resulting in a triangular construction. The rigidity of this arrangement was found to be undesireable, so the 1913-1914 electrification extension to New Haven utilized a single messenger wire, as did other extensions. The system reached 673 track miles at its maximum.

The Cos Cob Power Plant was the first power plant built exclusively for a railroad and is considered an engineering achievement for its use of high-voltage alternating current (ac) for railroad electrification. The plant served the New Haven Railroad until the railroad's demise in 1969, and then served Penn Central, Conrail and Metro-North until it was closed in 1986. The Cos Cob Power Plant received landmark status from the American Society of Mechanical Engineers/Institute of Electrical and Electronics Engineers in 1982.


18 Linear Feet

Language of Materials



The Cos Cob Power Plant, an electrical power plant located in Greenwich, Connecticut, was part of a pioneering venture in mainline railroad electrification. With the Westinghouse Electric and Manufacturing Company, the New York, New Haven & Hartford Railroad designed an efficient system using alternating-current (ac) electrification that facilitated railroad traffic into urban areas after the New York legislature passed laws prohibiting the use of steam locomotives in New York City south of the Harlem River. Construction of the Cos Cob Power Plant was completed in 1907 and served as the generating station for power to the trains. The collection consists of blueprints and wiring diagrams for the electrical systems of the Woodlawn, New York, to New Haven, Connecticut, line, with architectural drawings, foremen's log books, records of coal received, and administrative correspondence.


Series I: Blueprints and other documents (1912-1966) of anchor bridges and electrification along the New Haven Railroad shoreline route from New York City to Cedar Hill in New Haven, Connecticut, . Materials in this series are organized by anchor bridges (or electric girders which support the catenary wire that transmits the electricity) situated along the electrified railroad zone.

Series II: Historical information about electrification along the New Haven Railroad (1891-1982) provides information about the equipment and structures serviced and the processes that were made possible through the Cos Cob Power Plant, mostly in its first several years of function.

Series III: Boiler office records concerning machinery (undated, 1915-1986) give detailed information about the servicing of equipment through the boiler office of the plant.

Series IV: Boiler office files (undated, 1921-1985) consist of manuals, catalogs, and instructions for boilers and circuit breakers, as well as correspondence, inventories, blueprints, and other documents with information about environmental pollution and emissions monitoring, labor unions for the railroad personnel, and specifications for switchboards, cable, and transformers. Also includes photographs of exterior and interior scenes of the plant and its equipment, as well as the Mianus pumping station and company executives. Alphabetically by topic.

Series V: Boiler office log sheets and repair records (1926-1986) show regular service and repair notes for the boiler room, coal received, the operations foreman, and electric meter field tests.

Series VI: Power plant architectural plans (rolled plans) (undated) show maps of the power plant property and plans and details of the power plant facilities and the Mianus River Dam.

Custodial History

The records were stored in the power plant facility in Cos Cob, Connecticut, prior to the donation to the University of Connecticut.

Acquisition Information

The Cos Cob Power Plant Records were transferred from the Connecticut Department of Transportation to the University of Connecticut Library in August 1988 and March 1991.

Existence and Location of Copies

Digital reproductions of materials in this collection may also be found in the Archives & Special Collections digital repository

Cos Cob Power Plant Records
Archives & Special Collections staff
2003 November
Description rules
Describing Archives: A Content Standard
Language of description
Script of description
This finding aid was prepared with generous support from the Eldon and Judith Bernstein Endowment.

Repository Details

Part of the Archives and Special Collections, University of Connecticut Library Repository

University of Connecticut Library
405 Babbidge Road Unit 1205
Storrs Connecticut 06269-1205 USA US