The United States Secretary of the Interior is the head of the United States Department of the Interior, founded in 1849. The Department of the Interior oversees such agencies as the Bureau of Land Management, the United States Geological Survey, and the National Park Service. The Secretary also serves on and appoints the private citizens on the National Park Foundation board. The Secretary is a member of the President's Cabinet and is eighth in the presidential line of succession.

While the Department of the Interior hasn't been front and center in Harry Turtledove's work, he has been known to make fictional use of it.

Southern Victory

Secretary of the Interior Term Party President
Henry Wallace GeorgeMarshall.jpg 1937-1942 Socialist Al Smith
Harry Hopkins Harry Lloyd Hopkins.jpg 1942-1945 Socialist Charles W. La Follette
Unknown Nophoto.jpg 1945-series' end Democrat Thomas Dewey

Literary comment

Some of the dates listed above are estimates. See also Inconsistencies in Turtledove's Work#Inconsistencies in Southern Victory.

Historical Secretaries in non-Secretarial roles

Zachariah Chandler appears in "Must and Shall" in his OTL role of Senator. Whether he later held a cabinet post is not revealed.

Lucius Q.C. Lamar appears in The Guns of the South, and plays an important background role in How Few Remain. In both timelines, he is a citizen of the independent Confederate States from the 1860s onward, making the question of his U.S. offices irrelevant.

Douglas McKay seems to be the unnamed Governor of Oregon referenced in The Hot War: Bombs Away. The series ends before the start of his OTL Secretarial tenure, which - given the national situation at series' end - is likely to be delayed at least a year if it happens at all.