NY 120 was assigned as part of the 1930 renumbering of state highways in New York, but only to the portion of its routing north of Westchester Avenue. It was extended south to Rye , then rerouted to follow Westchester Avenue east to Port Chester by the following year. Most of NY 120's former routing to Rye became part of New York State Route 119A at that time. NY 120 was rerouted to serve Rye again in October 1960, replacing NY 119A.