The exact origin is unknown, but many believe it was created by Italian immigrants who worked for Chicago's old Union Stock Yards in the early 1900s. They often would bring home some of the tougher, less desirable cuts of beef sold by the company. To make the meat more palatable, it was slow-roasted to make it more tender, then slow-simmered in a spicy broth for flavor. Both the roasting and the broth used Italian-style spices and herbs. The meat was then thinly sliced across the grain and stuffed into fresh Italian bread.