 The highway began at an intersection with US 20 and NY 321 in the village of Skaneateles and ended at a junction with US 20, NY 20N, and NY 92 near the village of Cazenovia.Most of NY 20SY overlapped another route; however, two sections of NY 20SY—one in the town of Camillus and another near the village of Fayetteville—were not concurrent with another highway.NY 20SY was assigned in 1951, overlapping parts of the pre-existing NY 321, NY 5, NY 92, and NY 20N, a more southerly alternate route of US 20 in the Syracuse area.