Mountain group of the Appalachian mountain system, southeastern New York, U.S. It is bounded by the Mohawk and Hudson rivers. Many of its peaks reach 3,000 ft (900 m); the highest, Slide Mountain, reaches 4,204 ft (1,281 m). The area has many resorts, and its lakes supply New York City with water. The mountains were made famous through Washington Irving's stories of Rip Van Winkle, who supposedly took his long nap near the town of Catskill.