Lewiston Dam is an earthfill dam on the Trinity River that forms Lewiston Lake near Weaverville, California, United States. The 91 ft high earthfill dam is 7 mi downstream of Trinity Dam and was built by the U.S. Bureau of Reclamation. Construction was completed in 1963. Lewiston Lake and Dam are part of the Central Valley Project, which harnesses the waters from the Sacramento River and San Joaquin River watersheds to irrigate the Central Valley, and provide hydroelectricity.