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)
August 19, 1932: “A snowdrift four feet in depth has so far withstood the attack of the summer sun at Slate peak lookout at the head of the west fork of the Pasayten river, according to Roy Paul, who is stationed at that point. Paul arrived in Winthrop about 1 o'clock Wednesday night for dental work, and returned to the lookout Thursday. During his stay at the station this summer Paul has experienced almost every variety of weather he says. The early months brought cold nights and bleak, threatening days. High temperatures arrived about a week ago,and he reports the remaining snow is melting quite rapidly. Two weeks ago a snowstorm swept the high country, and the station perched on the 7438 foot summit was plunged into winter. A few fires, all in the Canadian forest were sighted from Slate peak. To date none have occurred in the portion of the Chelan and Mt. Baker forests surrounding the peak.” (The Wenatchee Daily World)
August 27, 1932: “Ray Paul, lookout stationed on Slate peak in the northern part of the Chelan National forest, arrived home from a long trip yesterday just in time to be an unwilling host to a stray lightning bolt, which came in, apparently, to seek shelter from the storm. Shattering the wire cage designed to protect the new lookout stations from such visitations, the bolt damaged the roof, played havoc with the telephone and set Paul's bed afire. The forester extinguished the blaze with a bucket of water but was unable to rescue a $15 Pendleton blanket. The Slate peak station is of a type is nearly lightning proof as can be obtained, according to H. F. Brundage, assistant regional forester in charge of forest protection. The walls are almost entirely of glass, surrounded by a wire cage designed to intercept lightning.” (The Wenatchee Daily World)
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.