The route ran northeast through the dense woods along Sweet Road, climbing up the hills of Fulton County south of the Adirondack Park to a junction with North Bush Road, where it turned eastward along North Bush.

Along North Bush, NY 399 passed a cemetery and local radio tower.

This new state highway would also allow Gloversville easier access to the western end of Fulton County.

[3] On two occasions, the former alignment of NY 399 still maintained by the state was proposed as part of a highway maintenance swap.

[10] In January 1978, the state and the county agreed to a scaled-down swap that would allow the state to acquire CR 127 in return for former NY 399, East Fulton Street Extension in Gloversville and West Perth Road.