 The route was assigned in the early 1940s, replacing New York State Route 17D, a route established as part of the 1930 renumbering of state highways in New York. It originally began in downtown Elmira and ended at the Pennsylvania state line in Chemung. NY 427 was realigned on its east end in 1967 to meet the newly constructed exit 59 on NY 17 and on its west end in 1978 to follow what had been New York State Route 379 through the town of Southport. Other minor realignments have occurred over the years as well.
