High Quality Content by WIKIPEDIA articles! The Southern State Parkway (also known as Southern State or Southern Parkway) is a 25.53-mile (41.09 km) long limited-access highway on Long Island, in the U.S. state of New York. Southern State Parkway travels east from Elmont, in Nassau County, ending at its eastern terminus in West Islip, where Southern Parkway becomes Heckscher Parkway.