The East Branch Delaware River is one of two branches that form the Delaware River. It is approximately 75 mi (121 km) long, and flows through the U.S. state of New York. It winds through a mountainous area on the southwestern edge of Catskill Park in the Catskill Mountains for most of its course, before joining the West Branch along the northeast border of Pennsylvania with New York. For a long stretch it serves as the Blue Line, the park's boundary. Much of it is paralleled by State Route 30.