Pocantico River

The Pocantico River is a nine-mile-long (14 km) tributary of the Hudson River in western central Westchester County, New York, United States. It rises from Echo Lake in the town of New Castle south of the hamlet of Millwood, and flows generally southwest past Briarcliff Manor to its outlet at Sleepy Hollow. Portions of the towns of Mount Pleasant and Ossining are within its 16-square-mile (41 km²) watershed.

Writer Washington Irving, who lived in the area for most of his life, was inspired by the undeveloped area above the river's mouth to write his classic "The Legend of Sleepy Hollow". Later in the 19th century much of the land was purchased by the Rockefeller family as part of their Kykuit estate; today much of that land has become Rockefeller State Park Preserve. A former reservoir used by the city of New Rochelle has likewise been converted into county-run Pocantico Lake Park. While the river runs predominantly through those parks and suburban land, it is still one of the most polluted tributaries of the Hudson.

In the past the Pocantico was considered to have two different sources, but today it is acknowledged that it rises from Echo Lake in the town of New Castle between Saw Mill River Road (New York State Route 100) and the Taconic State Parkway, just southwest of the unincorporated hamlet of Millwood. The lake is 325 feet (99 m) above sea level, in a narrow valley between Cabin Ridge to the east and a similarly steep ridge on the west. Its surrounding terrain is primarily wooded and lightly developed outside of the two roads. The river begins at a dam on the lake's south end.

Shortly after draining the lake, the Pocantico flows under Route 100, which it remains closely parallel to for the next few miles. About 1,200 feet (370 m) from its source, the stream crosses the town line from New Castle into neighboring Ossining, soon forming the boundary between that town and neighboring Mount Pleasant on its west. A short distance to the south, the river crosses back under Saw Mill River Road and receives its first tributary, the unnamed outlet of Campfire Lake to the northeast, as it, Route 100 and the North County Trailway diverge from the Taconic. The river, road and trail continue heading to the southwest as the Pocantico begins to form the Briarcliff Manor village line at the Chappaqua Road crossing.

Another 1,200 feet south of that crossing, it recrosses Saw Mill River Road just north of where it merges with the Briarcliff–Peekskill Parkway (also State Route 9A). After flowing under the parkway, it passes just east of downtown Briarcliff Manor and then crosses Saw Mill River Road and the parkway again, meandering a little further to the east into residential neighborhoods, then turning south through the village's Jackson Road Park. After that it flows due south to the immediate east of the parkway, itself to the immediate east of a steep slope.

After a slight swing east towards the Taconic, the river crosses under the parkway for the last time and continues on a more southwesterly course past 420-foot (130 m) Beech Hill into 164-acre (66 ha) Pocantico Lake Park. It widens amid swampy areas on either side as it receives Caney Brook from the north and then becomes Pocantico Lake. Midway along the lake, the municipal boundary leaves the river, putting it entirely within the town of Mount Pleasant. The dam at the lake's south end is at 219 feet (67 m) above sea level, a loss of 106 feet (32 m) from the Pocantico's source at Echo Lake.

From there, it flows southwestward again. At Old Sleepy Hollow Road it enters Rockefeller State Park Preserve, at over 1,400 acres (570 ha) the largest of the three protected areas the river flows through. The road continues to parallel it on the east as it turns south; on the west it is paralleled by the preserve's Pocantico River Trail, which follows it for a mile and a half (2.4 km). All three cross under Phelps Way (State Route 117) and turn south.

Within the preserve, the river meanders between hills amidst woodland interrupted by large clearings. Small stone bridges (built by the Rockefellers) carry several of the preserve's trails across the river. About 600 feet (180 m) after entering the preserve, the Pocantico crosses into the village of Sleepy Hollow. A short distance to the south, it receives Rockefeller Creek from the Pocantico Hills to the east. It bends north, away from the road, to receive its last named tributary, Gory Brook, from the north, where it turns abruptly south again. After another quarter-mile (400 m) it passes under the massive Mill River Culvert of the Old Croton Aqueduct, and leaves the preserve, continuing straight through a steep, narrow wooded ravine in a slightly southwesterly direction.