Reserve is located at (45.859877, -91.372722) [REF].
According to the United States Census Bureau, the CDP has a total area of 53.7 square miles (139.1 km²), of which, 53.0 square miles (137.3 km²) of it is land and 0.7 square miles (1.8 km²) of it (1.30%) is water.