Documents and letters relating to Ambrose N. Armstrong's activities as deputy surveyor in Oregon Territory and as a major of the Oregon Mounted Volunteers during the Native American conflict of the Cayuse War. Includes: field notes for survey of a tract of land; commission of Armstrong; special instructions; orders; letter from Colonel J.W. Nesmith to Armstrong regarding reinforcements for Walla Walla; and letter from Governor George S. Curry to Armstrong accepting his resignation due to poor health. Of special interest is the letter of November 21, 1855, which includes instructions on treatment of Native Americans in the military campaign.