The New York State Legislature created Route 3-a, an unsigned legislative route extending from Port Jervis to Hancock along the Delaware River, in 1911. Initially, it was a route in name only as the portion north of Port Jervis had yet to be built. Several parts of the route were constructed during the 1920s, and by the time the NY 97 designation was created as part of the 1930 renumbering of state highways in New York, only two sections were still unconstructed. The entirety of the highway officially opened on August 30, 1939, capping a construction project that cost $4 million (equivalent to $ in ) to complete.