Manuscript diaries (13 vols., 1895-1900) regarding the Thunder Mountain Mining District, Valley County, Idaho; photographs of Caswell family members and Valley County scenes; typed transcriptions of the diaries; and related materials.

Correspondence, articles of incorporation, and stock certificates relating to the Thunder Mountain Gold Mining Company and the Home Mining and Milling Company, Ltd., companies served as Dunlop as director. Also included are receipts from S.J. Dunlop and Company, a Spokane Falls, Washington, meat supplier; newspaper clippings relating to the Thunder Mountain gold fields; and photographs of mining towns and activities.