The Aircraft Warning Service Observation Tower in Agnew, Washington was built in 1941 as a spotting station for Aircraft Warning Service volunteers watching for intruding Japanese airplanes during World War II.

The 35-foot (11 m) wood-frame tower was built from donated materials behind the Fred and Jean Cook farmhouse, overlooking the Strait of Juan de Fuca.

Jean Cook, as "chief observer," organized a team of 300 people to maintain a 24-hour watch.

The Cook tower is the only remaining such facility in Clallam County, Washington.

Owing to liability concerns, the tower was partially dismantled and moved to the property of Harriet U.