Lower Monumental Dam

The Lower Monumental Dam is a concrete barrier crossing the Snake River, designed to generate power while allowing river traffic to pass through. The structure includes spillway gates for water release and a navigation lock that accommodates cargo vessels and other watercraft.

The U.S. Army Corps of Engineers started building this structure in 1961, with power generation beginning in the late 1960s. Additional generating units were installed over the following years to increase the facility's electricity output.

The dam forms Lake Herbert G. West, which extends 28 miles eastward and provides opportunities for fishing, boating, and wildlife observation.

You can view the structure from observation areas located along the riverbanks. Daytime visits offer the clearest views of the dam and its surroundings.

The navigation lock system features a single lift mechanism with dimensions of 86 feet in width and 666 feet in length.

Location: Walla Walla County

Inception: 1961

Length: 1,155 m

GPS coordinates: 46.56240,-118.53700

Latest update: December 12, 2025 07:56