c.1920: The lookout was established with a log cabin for shelter.
1923: A D-6 cupola style lookout house was constructed.
September 1925: "When Walter Metcalf and two other men from the Chewach road camp found themselves hard pressed to hold an 18-acre fire on Disaster Creek they signaled an S.O.S. to the 20-Mile lookout by using a polished lard pail cover to flash the signals in Morse code. The lookout then signaled back to them that help was on the way. Reinforcements has been started an hour hour before their message was received." (Six Twenty-Six)
September 1925: "Percy Huston, lookout on Twenty Mile, says, 'A fire a day keeps the monotony away.' If this be true, life on Twenty Mile must be extremely interesting these past few days, with fresh thunderstorms and fires every day. Perry's favorite method of penetrating the smoke haze is to pick up the fires at night by the glow. Nobody seems to know when he sleeps. P.T.H." (Six twenty-Six)
July 14, 1926:"Another bad fire in the Chelan forest was reported yesterday near the Twenty-Mile lookout station. Already it covers 1000 acres, has become a crown fire and is being spread rapidly by a stiff wind. Last reports showed that it had traveled two miles in four hours. It is threatening a valuable stand of yellow pine and is also threatening to wipe out the North Twenty-Mile lookout station. Dry electric storm yesterday started in the Chelan forest four class 'C' fires or fires of more than ten acres, and eight class 'A' fires, those less than a quarter of an acre." (The Oregonian)
February 1929: "A very handy little 'etcher' was shown me when I visited North Twenty-Mile Lookout in the Winthrop District. Neither Ranger Burge nor his star lookout man, Carl Albin, have said anything about it in the pages of Six Twenty-Six, so, figuratively speaking, I am going to take their light from under the bushel and set it upon the table that all in the house may see. It was a piece of window glass, three inches square, on which had been etched lines and figures the same as on township plat of one-half inch to the mile scale. When Carl spotted a fire, he laid the glass on the township on his fire finder map in which he reported the fire. By eliminating the necessity of counting, it enabled him quickly and accurately to determine the section. Also, the danger of mistaking a longitudinal or meridional line for a section line was reduced to a mere possibility. Celluloid would be probably just as good as the glass and would be easier to mark. "Etchers' could be marked for any scale map on which they were to be used. S.R. Woods" (Six Twenty-Six)
1947: A 30-foot treated timber tower with an L-4 cab was erected.
National Geodetic Survey
DESIGNATION - NORTH TWENTYMILE LOOKOUT HOUSE PID - TQ0428 STATE/COUNTY- WA/OKANOGAN COUNTRY - US USGS QUAD - COLEMAN PEAK (1969)
DESCRIBED BY COAST AND GEODETIC SURVEY 1925 ON THE SUMMIT OF NORTH TWENTY MILE PEAK ABOUT 20 MILES NORTHEAST OF WINTHROP, WASHINGTON. IT MAY BE REACHED FROM WINTHROP BY ROAD 18 MILES UP THE CHEWACK RIVER, THENCE FOLLOWING THE FOREST SERVICE TRAIL AND TELEPHONE LINE UP TWENTY MILE CREEK TO THE STATION. A STANDARD REGION-6 U.S. FOREST SERVICE LOOKOUT HOUSE WITH PEAKED CUPOLA STANDS ON THE SUMMIT OF THE PEAK. THE STATION WAS NOT OCCUPIED.
STATION MARK--THE APEX OF THE CUPOLA OF THE LOOKOUT HOUSE. NO COAST AND GEODETIC SURVEY BRONZE-DISK STATION MARK WAS SET AT THE TIME BUT THE FOREST SERVICE STATES THAT ONE WILL BE SET IN THE LEDGE UNDER THE FLOOR OF THE HOUSE, DIRECTLY UNDER THE CENTER OF THE CUPOLA. A BRONZE DISK OF THE U.S. FOREST SERVICE LETTERED U.S. FOREST SERVICE, DEPARTMENT OF AGRICULTURE, WAS SET IN A BOULDER ABOUT 6 FEET LONG BY 3 FEET HIGH, IN AZIMUTH 191 DEG 46 MIN, 49.49 METERS FROM THE CENTER OF THE CUPOLA AS PROJECTED TO THE GROUND. (INTERNATIONAL BOUNDARY COMMISSION REPORT).