According to Wikipedia, 'Marilyn Brown, Director of the Consumer Test Kitchen at H.J. Heinz in Pittsburgh, says their research at the Carnegie Library suggests that the sloppy joe's origins lie with the "loose meat sandwiches" sold in Sioux City, Iowa, in the 1930s and were the creation of a cook named Joe.' Today, sloppy joe's are usually made of ground or shredded beef or pork in a tomato sauce.