Technical Abstract: Identifying the reservoirs of a pathogen is vital for control of sporadic disease and epidemics. Listeria monocytogenes is a zoonotic food-borne pathogen that is responsible for 28% of food-related deaths in the United States annually, as well as a major cause of massive product recalls worldwide. Because this bacterium is capable of surviving under a wide range of environmental conditions and growth at refrigeration temperatures, it is a significant problem to the food processing industry. Although listeriosis is a zoonotic disease, the primary reservoir of L. monocytogenes in food processing plants is believed to be environmental strains that colonize the plants. In this report we demonstrate that a strain of L. monocytogenes responsible for the 1985 California epidemic continues to cause sporadic illness and has a dairy farm reservoir.