New York State Route 100A

New York State Route 100A
Map of Westchester County in southeastern New York with NY 100A highlighted in red
Route information
Auxiliary route of NY 100
Maintained by NYSDOT
Length	4.21 mi[1] (6.78 km)
Existed	1930[citation needed]–present
Major junctions
South end	NY 100 in Hartsdale
Major intersections	I-287 in Elmsford
North end	NY 100 / NY 100C / Sprain Brook Parkway at the Greenburgh–Mount Pleasant line
Location
Country	United States
State	New York
Counties	Westchester
Highway system
New York Highways Interstate US State Reference Parkways
← NY 100 → NY 100B

New York State Route 100A (NY 100A) is a 4.21-mile (6.78 km) loop route of NY 100 in Westchester County, New York, in the United States. It follows West Hartsdale Avenue and Knollwood Road in the town of Greenburgh. The route starts in the hamlet of Hartsdale and ends in the community of Grasslands at the boundary between the towns of Greenburgh and Mount Pleasant.