1924: A gable-roof cabin with a cupola was constructed.
September 3, 1931: “Ed Allen and Raymond Johnson left Tuesday for the mountains where they will complete the work on the lookout house at Slate Peak.” (The Wenatchee Daily World)
September 1931: "Slate Peak, a lookout-fireman's point on the Chelan near Harts Pass, was occupied for the first time this year. We immediately took advantage of this occupancy and strung some eight miles of emergency wire to connect with this point. A couple weeks ago, said lookout reported a fire on Upper Slate Creek; it probably would have got to some size before our nearest lookout might have picked it up. As it was we has a man to it in a short time -- result: a class A fire. Thanks, Chelan -- hope we may return the help some day. L.B. Pagter" (Six Twenty-Six)
Activated: March 30, 1942; Deactivated: September 19, 1942. Seattle Filter Center.
1954: A 14 x 14 L-4 cab was moved to the peak from Leecher Mountain.
1956: A new 41-foot treated timber tower with an L-4 cab was erected.
1956: The U.S. Air Force took control of @119 acres on the top of the peak. The lookout cabin was removed along with approximately 40 feet of the mountain top, leaving a level area for the construction of an unmanned Gap Filler radar site.
1960: The Annex was constructed and was subordinate to the Colville Air Force Station.
January 4, 1961: The radar annex was declared excess inventory.
October 23, 1961: A bid was accepted for the salvage of the improvements, buildings, underground fuel storage tanks and the radar tower.