Interstate 81 in New York

Interstate 81 (I-81) is a part of the Interstate Highway System that runs from I-40 at Dandridge, Tennessee, to the Thousand Islands Bridge at Wellesley Island in New York, beyond which the short 2.7-mile (4.3 km) Ontario Highway 137 (Highway 137) links it to Highway 401. In the US state of New York, I-81 extends 183.60 miles (295.48 km) from the Pennsylvania state line southeast of Binghamton to the Canadian border at Wellesley Island northwest of Alexandria Bay. The freeway runs north–south through Central New York, serving the cities of Binghamton, Syracuse, and Watertown. It passes through the Thousand Islands in its final miles and crosses two bridges, both part of the series of bridges known as the Thousand Islands Bridge.

South of Watertown, I-81 closely parallels US Route 11 (US 11), the main north–south highway in Central New York prior to the construction of I-81. At Watertown, US 11 turns northeastward to head across New York's North Country region while I-81 continues on a generally northward track to the Canadian border. From there, the road continues into the province of Ontario as Highway 137, a short route leading north to the nearby Highway 401.

The portion of I-81 in New York was originally developed as the Penn-Can Highway, one of four expressways proposed by the state in 1953. It was added to the Interstate Highway System and designated I-81 in 1957 and constructed in sections over the course of the next decade. The first segment was completed in the mid-1950s, running from Tully to the southern edge of Syracuse. The last piece opened in the late 1960s, linking Marathon to Whitney Point.