Abstract: Papers of Cyrus Hall McCormick, inventor of the reaper and a Chicago industrialist, comprising correspondence, memoranda, and letterbooks concerning the growth of the McCormick Harvesting Machine Company in both the domestic and foreign fields, and dealing with McCormick's many other interests, particularly the Presbyterian Church and several charities; his activities as a member of the state and national Democratic party; and his investments, chiefly in Chicago real estate, railroads, and mines. Also included are deeds, contracts, investment proposals, and other documents. Some of the letters are to or from McCormick's wife Nettie Fowler, their son Cyrus Jr., and others associated with the McCormick Harvesting Machine Company. The earliest dated items were written or received by Cyrus' father, Robert McCormick, and by other family members.