In 1908, the New York State Legislature created Route 5, an unsigned legislative route that extended from Kingston in the south to Mohawk in the north.
When the first set of posted routes in New York were assigned in 1924, the Oneonta-Grand Gorge segment of legislative Route 5 and all of Route 47 became part of NY 23, which continued east from Catskill to the Massachusetts state line southwest of Great Barrington, Massachusetts.