Custer Peak Fire Lookout was built in 1911. In 1935 it was replaced with a cupola building, and in 1941 the Civilian Conservation Corps used local natural materials to construct the fire lookout you see today.
The structure was designed by architect William Ellis Groben. He was the office architect for the U.S. Forest Service from 1933-1953. The cab is 14 ft. by 14 ft. surrounded by a catwalk. Originally, the tower had a telephone line that ran between Custer Peak and the Bull Dog Ranch.
The tower is considered eligible for the National Register of Historic Places. It was listed on the National Historic Lookout Register on Oct. 13, 1990.
Source: https://www.fs.usda.gov/recarea/blackhills/recarea/?recid=82116
Photos from my hike up to the Fire Lookout