The Oyster Bay Branch is a rail line and service owned and operated by the Long Island Rail Road in the U.S. state of New York. The branch splits from the Main Line just east of Mineola station, and runs north and east to Oyster Bay. The branch is electrified between East Williston and Mineola. The branch opened in segments between 1865 and 1889.

The Main Line is a rail line owned and operated by the Long Island Rail Road in the U.S. state of New York. It begins as a two-track line at Long Island City station in Long Island City, Queens, and runs along the middle of Long Island about 95 miles (153 km) to Greenport station in Greenport, Suffolk County. At Harold Interlocking approximately one mile east of Long Island City, the tracks from the East River Tunnels and 63rd Street Tunnel into Manhattan intersect with the Main Line, which most trains use rather than using the Long Island City station.