Keystone Mushroom Farms, Inc. was a producer, canner, and distributer of mushrooms in Coatesville, Chester County, Pennsylvania. It was the successor of two previous businesses, L.F. Lambert Spawn Co. and Keystone Mushroom Company, Inc., which were formed in the early 1920s with complementary functions of spawn research; production and sales; and mushroom propagation, canning, and distribution. These records document the L.F. Lambert Spawn Co. and the Keystone Mushroom Company, Inc. The collection includes financial records, correspondence, payroll, reports, and shipment and inventory information. Of special interest are the records documenting Lambert's work with the War Production Board to produce penicillin.