Electrification of the New York, New Haven and Hartford Railroad
The New York, New Haven and Hartford Railroad pioneered electrification of main line railroads using high-voltage, alternating current, single-phase overhead catenary. It electrified its mainline between Stamford, Connecticut, and Woodlawn, New York, in 1907 and extended the electrification to New Haven, Connecticut, in 1914.
Source: Wikipedia — Electrification of the New York, New Haven and Hartford Railroad (CC BY-SA 4.0)