According to the United States Census Bureau, the town has a total area of 66.6 square miles (172.5 km²), of which, 59.3 square miles (153.6 km²) of it is land and 7.3 square miles (19.0 km²) of it (10.99%) is water.
The west border of the town is Lake Ontario and the south border is formed by the Black River, which flows into the lake at Black River Bay.