The Seaway Trail enters Cayuga County heading northeast along Route 104A and soon enters the village of Fair Haven, on the southern shore of Little Sodus Bay. Route 104A turns east toward the hamlet of Sterling, then north again before again moving northeast, paralleling the Lake Ontario shore at a distance of about two miles (3.5 km). Just a mile later, Route 104A hits the county line. Continuing northeast, Route 104A terminates at its parent route, NY 104, which previously carried the Seaway Trail in Niagara Falls and here does so again. Route 104 continues Route 104A's northeastern path, gradually getting closer to the lake shore, until it enters the city of Oswego. Crossing the Oswego River, Route 104 continues eastward.