Union Station served the residents of Chatham, New York, from 1887 to 1972 as a passenger station and until 1976 as a freight station. It was the final stop for Harlem Line trains. It had originally served trains of the Boston and Albany Railroad, then the New York Central Railroad and the Rutland Railway. It served as a junction for service that radiated to Rensselaer, New York, to the northwest; Hudson, New York, to the southwest; Vermont, to the northeast, and Pittsfield, Massachusetts to the east and New York City, to the south.

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.