Abstract: Domestic and foreign correspondence and reports received by the McCormick Harvesting Machine Company (1879-1902) and its predecessors, C.H. McCormick and Co. (1848-1859), C.H. McCormick & Bros. (1859-1866), C.H. McCormick & Bro. (1866-1874), and C.H. and L.J. McCormick (1874-1879). Included are letters from company agents, field experts, shippers, suppliers and customers regarding orders, sales, credit, shipments, price and performance of machines and repairs, field trials, improvements and inventions, competition in the implement business, crop yields and damage due to insects and weather, rural and foreign economic conditions, travel and branch office expenses, and employment opportunities. Letters, legal documents, drawings, and plans from patent experts and inventors concern cases of infringement, experimental machines, the design of new devices, and proposed improvements. Reports from agents are primarily contracts and financial accounts of machine sales, deliveries, and inventories, debt collection, and expenses. Among the subjects documented are the structure and activities of the company's domestic and foreign sales force, the market for farm machinery, the expansion of trade, customer relations, activities of the Grange and the company's response, and patent issues. While most of the correspondence is addressed to the company's home office in Chicago, Illinois, a small portion of the letters are directed to a particular manager or official. Copies of outgoing letters are sometimes found in this series, particularly in later years. A small amount (0.4 c.f.) of original correspondence, reports, and patent drawings has been retained for exhibit purposes.