It has only one other junction with a signed state highway, that being NY 170A, its spur route in the town of Fairfield.

NY 170 was assigned as part of the 1930 renumbering of state highways in New York and has not been altered since.

[3] Still in the town of Little Falls, NY 170 crosses under power lines, crossing an intersection with Top Notch Road (CR 126) and Yellow Church Road (CR 92).

[3] The origins of NY 170 date back to the mid-1910s when the portion of the route outside of Little Falls was first brought up to state highway standards.

[6] Most of what became NY 170A was added to the state highway system in the 1920s; however, the northernmost 1.24 miles (2.00 km) were added on October 11, 1912, as part of a larger project that rebuilt a 4-mile (6.4 km) section of modern NY 29.