Sombrero Butte is now a ghost town in eastern Pinal County near the Graham County line. Chester Proebstel and his family lived there from 1929 to 1932 while he served as superintendent of the mine operated by the Bunker Hill Mining Company of Portland, Oregon. Proebstel and his wife, Elta, lived in Sombrero Butte, and their four children - Norman, Walter, Lloyd, and Lenore attended the one-room school there.
From the description of Sombrero Butte papers, 1929-1996 (bulk 1929-1932.) (Arizona Historical Society, Southern Arizona Division). WorldCat record id: 40614181