NY 240 was assigned as part of the 1930 renumbering of state highways in New York to an alignment extending from NY 39 east of Springville to NY 18 southeast of downtown Buffalo. Instead of turning north onto Harlem Road as it does today, NY 240 continued northwest on Potter and Abbott Roads to South Park Avenue (then NY 18). At the time, the portion of modern NY 240 south of Cattaraugus Street in Springville was designated as part of NY 62 while the portion south of CR 16 in West Valley was also part of NY 242. NY 242 was moved onto its modern routing between Ashford and Machias by the following year while NY 62 was mostly renumbered to NY 75 .