 US 4 was assigned in 1926 and initially extended from Glens Falls to the Vermont border near Whitehall by way of Hudson Falls. The route utilized part of NY 6 and NY 30, two highways assigned in 1924. US 4 was extended southward to its present terminus in East Greenbush as part of the 1930 renumbering of state highways in New York. Much of US 4 south of Hudson Falls initially overlapped with other routes; most of the overlaps were gradually eliminated during the 1940s and 1950s as the concurrent routes were eliminated or truncated. At one time, US 4 overlapped with NY 32 from Waterford to Northumberland with no interruption in between. The concurrency was split into two shorter overlaps when US 4 was realigned in the 1950s to follow its current alignment between Bemis Heights and Schuylerville.
