Peterbilt Motors Company, founded in 1939, is an American manufacturer of medium- and heavy-duty Class 5 through Class 8 trucks headquartered in Denton, Texas. Peterbilt operates manufacturing facilities in Denton, Texas (1980), and Sainte-Thérèse, Quebec. From the early 1960s until the mid-1980s, the company was based in the San Francisco Bay Area of Northern California, with its headquarters, and main plant all in Newark, California. The original plant was in Oakland and closed in 1960.