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 (or "freeway") 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.