NY 40 was assigned as part of the 1930 renumbering of state highways in New York to an alignment extending from East Greenbush in the south to Comstock in the north via the city of Troy and the hamlet of Middle Granville. It began at U.S. Route 9 and U.S. Route 20 and ran concurrent with U.S. Route 4 to Troy, where it split from US 4 at 125th Street. From there, it followed 125th Street, Northern Drive, and Brickyard Road out of the city. NY 40 joined its modern alignment shortly afterward at Leversee Road.