The Harlem Line is an 82-mile (132 km) commuter rail line owned and operated by the Metro-North Railroad in the U.S. state of New York. It runs north from New York City to Wassaic, in eastern Dutchess County. The lower 53 miles (85 km) from Grand Central Terminal to Southeast, in Putnam County, is electrified with a third rail and has at least two tracks. The section north of Southeast is a non-electrified single-track line served by diesel locomotives. Before the renaming of the line in 1983, it eventually became the Harlem Division of the New York Central Railroad. The diesel trains usually run as a shuttle on the northern end of the line, except for rush-hour express trains in the peak direction.

Metro-North Railroad, trading as MTA Metro-North Railroad, is a suburban commuter rail service operated by the Metropolitan Transportation Authority (MTA), a public authority of the U.S. state of New York. Metro-North serves the New York Metropolitan Area, running service between New York City and its northern suburbs in New York and Connecticut, including Port Jervis, Spring Valley, Poughkeepsie, Yonkers, New Rochelle, Mount Vernon, White Plains, Southeast and Wassaic in New York and Stamford, New Canaan, Danbury, Bridgeport, Waterbury, and New Haven in Connecticut. Service in Connecticut is operated under contract with the Connecticut Department of Transportation. Metro-North also provides local rail service within the New York City boroughs of Manhattan and the Bronx.