Tacoma City Light's Mossyrock Dam on the Cowlitz River generates electricity on October 13, 1968.

  • By David Wilma
  • Posted 12/16/2002
  • HistoryLink.org Essay 5026

On October 13, 1968, Tacoma City Light’s Mossyrock Dam on the Cowlitz River in eastern Lewis County generates electricity for the first time. Mossyrock is the second of two large dams on the Cowlitz that were planned in the 1940s. Opposition from anglers and from the State Game Department delayed construction until 1965. The Cowlitz project will include two $20-million fish hatcheries.

During World War II, Tacoma had to buy power from the Bonneville Power Administration and from Seattle, which cost $1 million each year. Until that time, hydroelectric dams were viewed in the Northwest almost as a patriotic act and power shortages after the war demonstrated the pressing need for more. Tacoma built two dams during the war and added generators to existing hydro and steam facilities. Even before the war ended, Tacoma City Light started looking for new sites for hydropower. The Cowlitz River in Lewis County was selected and the City announced its plans in 1948. Construction was to have taken “three or four years” (Malloy, 172).

Opposition rose immediately from sportsmen’s groups and from the State Game Department. A state legislator introduced legislation authorizing the department to dynamite Tacoma’s Cushman dams because the dams lacked fish ladders (the measure died). The legislature did establish a fish sanctuary on the Cowlitz that blocked the project. Tacoma went to court and the matter went to the U.S. Supreme Court three times before the city prevailed.

Mayfield was completed in 1963. Mossyrock was a concrete arch design, 1,300 feet long and 325 feet high. The reservoir extended 21 miles up the Cowlitz River. The two generators in the powerhouse each generated 150,000 kilowatts of electricity for Tacoma.


Dick Malloy and John S. Ott, The Tacoma Public Utilities Story (Tacoma: Tacoma Public Utilities, 1993), 178-183, 220-222.

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