User:Daniel Case/sandbox

Course
The river rises from a 1.75 acre pond in a wooded area of the town of New Castle roughly 2 miles (3.2 km) north of Chappaqua, a half-mile (800 m) west of Quaker Road State Route 120 (NY 120) and just south of Stony Hollow Road, at an elevation of 490 ft above sea level. It wends and meanders past a cemetery, between hills, through a residential area of houses on large wooded lots in a generally southward direction. Just north of Marcourt Drive, its first crossing, it is impounded to create another small pond. After crossing under Kipp Street, it bends eastward to cross under Quaker Road.

A short channelized portion runs through the front yard of a large house on Quaker southeast of the intersection, after which the river flows back under Quaker and behind the houses on the west side into another impoundment, Chappaqua's Duck Pond. From its outlet it continues southeast between Quaker on its east and Douglas and Mill River roads on the west to the Saw Mill River Parkway. Just west of the Chappaqua train station, it turns southwest to parallel both the parkway and Metro-North Railroad's Harlem Line as both cross into the town of Mount Pleasant. At this point the river is at 340 ft in elevation, a loss of 150 ft from its source. Just south of the town line, it receives Tertia Brook, its first named tributary, from the east.

A mile past the town line they pass the unincorporated hamlet of Pleasantville to the east, where the river crosses under the parkway to flow on its west, crossing and recrossing again at the Pleasantville Road (State Route 117) exit. Both make a long turn to the southeast and then back to the southwest around Graham Hills County Park, where it receives its first named tributary, Nanny Hagen Brook, from the east, before crossing back to the parkway's west in the flood plain around the base of the hills as road, river and rail pass the hamlets of Thornwood, and Hawthorne, where the Harlem Line turns to the south.

Just east of the Taconic State Parkway, the river again crosses under the Saw Mill Parkway, then the Taconic. Shortly after that exit it crosses under Saw Mill River Road (State Routes 9A and 100) and some of the ramps to them from the interchange, then under the Saw Mill Parkway. Both turn south again, then southeast, following the eastern edge of the Pocantico Hills, joined on the west by the North County Trailway bike path, on the right-of-way of the former New York and Putnam Railroad, known as the "Old Put".

The river crosses under the parkway again to form the eastern edge of a plant nursery on Saw Mill River Road, then recrosses as the river, bike path, parkway and Saw Mill River Road all bend around the northwest corner of Eastview, where the Saw Mill drops below 200 ft in elevation, a loss of 100 ft since Chappaqua. and its vast office parks. A turn back to the southwest around Tarrytown Lakes County Park puts the river at the outskirts of Elmsford. There it receives Mine Brook from the east.

Here the bike path ends amidst the dense urban development, but the parkway continues, and the two again draw close as they enter the town of Greenburgh and intersect the Cross Westchester Expressway (Interstate 287). A new bike path, the South County Trailway, begins here just south of the West Main Street (State Route 119) bridge north of the Rum Brook confluence. Past that the parkway, trailway and river all turn southwest, where they intersect the New York State Thruway) (Interstate 87) at an oblique angle. For the next mile the Thruway remains close to the river, and Saw Mill River Road, now just carrying NY 9A, returns to the corridor just east of the Thruway as well.

This leads to V. Everit Macy Park on the west. As part of the park facilities, the Saw Mill River is impounded into Woodlands Lake, the largest impoundment on the river, used as a water supply by the local communities of Ardsley and Dobbs Ferry, whose northern villags line is just to the south. The river runs close to the boundary between the two, as the Thruway gradually veers away to the southeast just past the Ashford Avenue bridge.

Continuing south-southwest, the river along with the parkway and trailway enter Hastings-on-Hudson, its greenbelt the only major break in the village's dense suburban development. It slowly veers toward a more southerly heading, and enters the Nepera Park neighborhood of Yonkers after one mile (1.6 km), just south of Farragut Parkway. At Nepperhan, 1.5 miles (2 km) to the south, the parkway and the river diverge from each other after 16 mi. Saw Mill River Road continues to parallel its namesake.

Bending to the southwest again, the Saw Mill flows in a narrow channel through an industrial and commercial area. A mile south of the parkway, it flows through the middle of the former Smith Carpet Mills site, where it finally drops to 100 ft in elevation. After crossing Ashburton Avenue, the river bends around to flow briefly to the northwest under Nepperhan Avenue after crossing the Old Croton Aqueduct. It circles around War Memorial Field, giving up its remaining elevation as the Hudson River nears. the triangle between Nepperhan and Palisade avenues and School Street. At Van der Donck Park in downtown Yonkers, it resurfaces as it flows past the post office. For its final hundred feet (30 m), it re-enters a tunnel under the train station and the tracks of the Hudson Line, after which culverts empty it into the Hudson south of Dock Street.