New York State Route 345 (NY 345) is a state highway located entirely within St. Lawrence County in the North Country of New York in the United States. It is a north–south route connecting the towns of Waddington and Potsdam by way of the town of Madrid. The southern terminus of NY 345 is at an intersection with U.S. Route 11 (US 11) in the village of Potsdam. Its northern terminus is at a junction with NY 37 in the village of Waddington by the St. Lawrence River. NY 345 was assigned as part of the 1930 renumbering of state highways in New York; however, it originally followed a different alignment south of the hamlet of Madrid. At the time, what is now NY 345 between Madrid and Potsdam was part of NY 56A. The NY 56A designation was eliminated in 1980. NY 345 was realigned two years later to follow old NY 56A to Potsdam as a result of a highway maintenance swap between the state of New York and St. Lawrence County. Ownership and maintenance of NY 345's original routing south of Madrid was transferred from the state to the county and the village of Canton as part of the exchange. Route description NY 345 begins at an intersection with US 11 in the village of Potsdam, just north of Clarkson University. The route heads northwestward on Pine Street and Madrid Avenue as a village-maintained, state-numbered highway, crossing the CSX Transportation-owned St. Lawrence Subdivision by way of a grade crossing as it heads through a commercial and residential area. It exits the village shortly afterward, at which point the route becomes maintained by the New York State Department of Transportation. It heads northwestward on a linear path through the town of Potsdam, passing through mostly undeveloped areas comprising open fields and forests. NY 345 curves slightly northward at Burnham Corners before crossing Trout Brook and entering the town of Madrid, where it traverses the New York and Ogdensburg Railway by way of a grade crossing just outside the hamlet of Madrid. The highway continues into the community, where the route becomes Bridge Street and intersects NY 310 on the eastern bank of the Grasse River. It continues across the river to Main Street, at which point NY 345 turns to the northeast and follows Main Street out of the hamlet. North of Madrid, NY 345 curves back to