Map | Denning

The secluded Town of Denning, NY, is a hiking, skiing and fishing destination in the western part of Ulster County, bordering Sullivan County, deep within the mountains of Catskill State Park. Most full-time settlement is concentrated in and around the Hamlet of Sundown, by Rondout Creek, along the Neversink River, and between the two valleys northeast of Red Hill. Forests in the Sundown Wild Forest on the east side of town and in the Slide Mountain Wilderness Area in the central region are protected by New York’s Forest Reserve, contributing to Denning’s small human population. Visitors to town frequent the Catskill High Peaks of Peekamoose, Table and Lone Mountains in Sundown.

The Town of Denning, named for early landowner William Denning, was established in 1849, four years after the first school opened and 12 years after the arrival of the first known settler.


Blue Hole, Denning’s unmarked freshwater pool in Sundown Wild Forest, near the foot of Peekamoose Mountain, was once a little-known getaway for locals; however, in the past few years, word of its pristine beauty and tranquility spread across online travel communities, and Blue Hole began drawing up to 1,000 visitors per day. Now, the New York State Department of Environmental Conservation and other organizations have instituted measures and increased their vigilance to protect for future generations the natural assets of the Travel + LeisureAmerica’s Best Swimming Hole.’


Established: 1849
Total Area: 105.77 square miles
Elevation: 1,960 feet
Zip Code: 12740
Population (2010): 551


Blue Hole
Neversink River
Peekamoose Mountain
Red Hill Fire Observation Station
Rondout Creek
Sundown Wild Forest

Photos (L-R): Peekamoose | Snow Tubing – Frost Valley | Kayaking | Blue Hole