Fort Osage was an early 19th-century factory trading post run by the United States Government in western Missouri on the American frontier; it was located in present-day Sibley, Missouri. The Treaty of Fort Clark, signed with certain members of the Osage Nation in 1808, called for the United States to establish Fort Osage as a trading post and to protect the Osage from tribal enemies.

Factory was the common name during the medieval and early modern eras for an entrepôt – which was essentially an early form of free-trade zone or transshipment point. At a factory, local inhabitants could interact with foreign merchants, often known as factors. First established in Europe, factories eventually spread to many other parts of the world. The origin of the word factory is from Latin factorium 'place of doers, makers'.