 Ottawa Township was organized in 1858.The unincorporated community of Ottawa is located within Ottawa Township.According to the United States Census Bureau, the township has a total area of 15.3 square miles (39.7 km²), of which 15.1 square miles (39.1 km²) of it is land and 0.2 square miles (0.6 km²) of it (1.50%) is water.