Lower Monumental Lock and Dam is a hydroelectric, concrete, run-of-the-river dam in the northwest United States. Located on the lower Snake River in southeast Washington, it bridges Franklin and Walla Walla counties; it is six miles (10 km) south of Kahlotus and 43 miles (70 km) north of Walla Walla. Built and operated by the U.S. Army Corps of Engineers, Lower Monumental Dam is part of the Columbia River Basin system of dams. Navigation lock * Single-lift * Width: 86 ft (26 m) * Length: 666 ft (203 m)