King's Highway 137, commonly referred to as Highway 137, is a provincially maintained highway in the Canadian province of Ontario that serves to connect the northern end of Interstate 81 in New York with Highway 401, via the Canadian span of the Thousand Islands Bridge. While this road connected to the international bridge when it opened in August 1938, it was not designated as a King's Highway until 1965. Highway 137 passes through a portion of the Canadian Shield, a geographic feature which aided construction of the three Canadian spans of the Thousand Islands Bridge. These bridges, all of different designs, travel 538 m (1,765 ft) across the Saint Lawrence River. Highway 137 is 4.3 km (2.7 mi) in length and is located entirely within the United Counties of Leeds and Grenville.