From Washington To You
Concrete powerhouse and spillway of Lower Monumental Dam on the Snake River.
Photograph by the U.S. Army Corps of Engineers. Public domain.

From Washington to you

Lower Monumental Dam

Lower Monumental Dam · Walla Walla County · construction began 1961

The second Lower Snake dam is 3,791 feet long at river mile 41.6 near Kahlotus. Lake West runs 28 miles up to Little Goose.

Lower Monumental Lock and Dam was the second of four dams in the Lower Snake River Project, authorized in the Rivers and Harbors Act of 1945. Construction began in 1961. Three turbine units were operating in 1970. Three more came online in 1978.

The dam stands at Snake River mile 41.6 near Kahlotus. The Corps lists it as 3,791 feet long. Six 135-megawatt units total 810 megawatts. The project includes a powerhouse, spillway, navigation lock, and fish passage.

Lake Herbert G. West extends 28 miles upstream to Little Goose Dam. Authorized purposes are hydropower and navigation, with recreation, fish and wildlife, water quality, and irrigation as other purposes. The source below is the Corps Northwestern Division fact sheet.

  • Geography & Geology
  • History

Sources (1)

Last reviewed: September 21, 2026

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Lower Monumental Dam · From Washington To You