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.