Fay Clark worked for the St. Joe National Forest in 1912, the Missoula National Forest from 1913 to May, 1915, and then was promoted to administrator in control of construction work for the Regional Office in Missoula. He left the Forest Service in October, 1918 and did war work until October, 1919 when he returned to the Forest Service as Supervisor of the Deer Lodge National Forest in Butte. In September, 1922 he quit the Forest Service and became a professor at the University of Montana Forestry School. He retired from the University in 1955.
From the guide to the Fay G. Clark diaries, 1912-1952, (University of Montana-Missoula Maureen and Mike Mansfield Library Archives and Special Collections)