Founded in 1982, Petro's Chili & Chips, now known as Petro s, is a small fast-food chain that specializes in the Petro, which is a mixture of corn chips, chili, cheese, green onions, tomatoes and sour cream. It maintains locations only in the eastern third of the state of Tennessee. The concept was invented at the 1982 World's Fair in Knoxville, Tenn., where Petro's is still headquartered. The...