Phelps Hospital is located in Sleepy Hollow, a town in Westchester County, NY. It is about 25 miles north of New York City and adjacent to the Hudson River. By car: The Phelps campus is at the juncture of Route 9 and Route 117. Travelers from Rockland County may cross the Hudson River using the Tappan Zee Bridge, approximately 3 miles south of ....