New York State Route 100 (NY 100) is a major north–south state highway in Westchester County, New York, in the United States. It begins parallel to Interstate 87 (I-87) at a junction with the Cross County Parkway in the city of Yonkers and runs through most of the length of the county up to U.S. Route 202 (US 202) in the town of Somers. NY 100 was designated as part of the 1930 renumbering of state highways in New York. Prior to becoming a state road, various sections of NY 100 were part of several important early roads in the county.
Route description
NY 100 begins in the city of Yonkers as Central Park Avenue (almost always just called "Central Avenue") at exit 4 of the New York State Thruway (I-87). This portion of Central Avenue is maintained by Westchester County as County Route 47II (CR 47II), an unsigned reference route. Central Avenue continues south as a service road for I-87 until The Bronx, where it splits from I-87 shortly after entering the city, and becomes Jerome Avenue, a major surface road in the West Bronx. NY 100 diverges from I-87 just north of exit 5 and heads northeast, crossing over the Sprain Brook Parkway about beyond the split. Central Avenue has an interchange with Tuckahoe Road shortly after the Sprain Brook Parkway. The road continues through Yonkers in the area between the Grassy Sprain Reservoir and the Bronx River, with many shops lining both sides. At the northernmost part of the city, Central Avenue intersects Fort Hill Road, which leads to Jackson Avenue and the northbound Sprain Brook Parkway. Central Avenue continues out of the city of Yonkers into the Edgemont/Greenville section of the town of Greenburgh. The only noteworthy intersection in this area is with Ardsley Road, and east-west road that goes straight across most of south-central Westchester. NY 100 runs through the hamlet of Hartsdale, about two miles (3 km) north of the city line, and where the bypass route NY 100A (Hartsdale Avenue) begins. Hartsdale Avenue also continues east of the intersection into the village of Hartsdale without a route designation. Central Avenue then enters the city limits of White Plains, where the road ends at NY 119 (Tarrytown Road). Within White Plains, the road is county-maintained with unsigned designations of CR 99 and CR 90.
NY 100 north follows NY 119 west for a overlap through the western reaches of White Plains. Access to I-287 (the Cross-Westchester Expressway) and the Bronx River Parkway can be made in the vicinity of the 100/119 overlap. NY 100 then splits off to the north using Hillside Avenue and Grasslands Road as it goes around the perimeter of Westchester Community College. At a four-way intersection between Grasslands Road, Knollwood Road, and Bradhurst Avenue, NY 100 meets with the north end of NY 100A (Knollwood Road) and the east end of NY 100C. NY 100 makes a right-hand turn to follow Bradhurst Avenue north from the junction while Grasslands Road continues west as NY 100C. Bradhurst Avenue leads into the hamlet of Hawthorne within the town of Mount Pleasant, crossing over the Sprain Brook Parkway along the way. NY 100 subsequently shifts onto Briarcliff-Peekskill Parkway (NY 9A), a continuation of the Saw Mill River Road, after using a brief section of NY 141 (Broadway). From this junction, the parkway (carrying 9A and 100) is a limited-access highway as it continues north alongside the Taconic State Parkway. It has an interchange with NY 117 (Bedford Road) about north of the 9A/100 merge, with all exits and entrances on the left. 9A and 100 then enter the eastern edge of the village of Briarcliff Manor.
NY 100 then branches off on its own again in Briarcliff Manor, with NY 9A continuing north along the Briarcliff–Peekskill Parkway and NY 100 continuing northeast on the Saw Mill River Road, which roughly follows New York Central's old Putnam Division railroad. Many of the railroad's old stations can still be found along the highway. NY 100 passes through New Castle and meets NY 133 in the hamlet of Millwood, where access to the Taconic State Parkway can also be made. From here, NY 100 then follows the path of the Croton Turnpike (alternatively known in the area as Somerstown Turnpike and also as Saw Mill River Road). The road continues into the town of Yorktown, passing by the hamlet of Kitchawan. NY 100 then crosses the Croton Reservoir on Pines Bridge. After crossing the reservoir, NY 118 splits off to the west on Saw Mill River Road, while NY 100 continues northeast on the Croton Turnpike.