Lewis Township is a township in Union County, Pennsylvania, United States. The population was 1,405 at the 2000 census. Sand Bridge State Park a Pennsylvania state park is in Lewis Township along Pennsylvania Route 192. According to the United States Census Bureau, the township has a total area of 38.8 square miles (100.5 km²), of which, 38.7 square miles (100.3 km²) of it is land and 0.1 square miles (0.2 km²) of it (0.23%) is water. Lewis Township is bordered by Lycoming County to the north, West Buffalo and Limestone Townships to the east, Snyder County to the south and Hartley Township to the west.