Along the Lewis and Clark National Historic Trail Fort Osage National Historic Landmark.

This article focuses on Fort Osage National Historic Landmark in Sibley, Missouri, established in 1808 by William Clark as a military outpost and government trading factory following a treaty with the Osage Nation. The fort served to protect the Louisiana Territory, maintain political stability through alliances with local tribes, and facilitate trade, particularly with the Osages. Fort Osage was abandoned in 1827 after the U.S. government ended its Factory System, but it was later reconstructed in the mid-20th century based on archaeological and historical research. Today, the site operates as an educational and interpretive center along the Lewis and Clark National Historic Trail, offering programs that illustrate early 19th-century military and trading life. The fort is recognized as a National Historic Landmark and an archaeological district on the National Register of Historic Places.