This collection consists primarily of papers reflecting Oscar Baarson's work as a mining and civil engineer. Included are records (1928-1929) from his work for the Anaconda Copper Mining Company's East Helena Slag Treatment Plant; records (1933) from his work on the Sun River Bridge for the State Highway Commission; records (1935-1941) on his work as Helena City Engineer, including files on the Helena earthquakes of 1935, water system improvements, and street resurfacing; records (1949-1954) of his work checking construction plans for Montana state government buildings, including a renovation of the Montana State Capitol Building; and records (1955-1958) of his mine surveying work on the Valley View Group of mines near Townsend for Geominerals Corporation. There is also a small amount of family correspondence, and files concerning his teaching career in Idaho; the Masonic order; his work at Chuquicamata, Chile; and private surveying work. [Records of his work for the U.S. War Production Board are included in Manuscript Collection 239. Printed materials, photographs, and maps have been transferred to the Library, Photograph Archives, and Library Map Collection respectively.]