Lower Granite Lock and Dam is a concrete gravity run-of-the-river dam in the northwest United States. On the lower Snake River, it bridges Whitman and Garfield counties in southeastern Washington. The dam is located 22 miles (35 km) south of the town of Colfax, and 35 miles (56 km) north of Pomeroy.Lower Granite Dam is part of the Columbia River Basin system of dams. It was built and is operated by the United States Army Corps of Engineers.