Fort Union was a significant military outpost established in 1851, located near the confluence of the Missouri River and Fort Union Trading Post. It served as a key supply depot and a base for the U.S. Army during the westward expansion of the United States. The fort played a crucial role in protecting settlers and facilitating trade in the region. The fort was strategically positioned to support military operations and maintain peace among various Native American tribes. It was abandoned in 1891, and today, the site is preserved as a historic landmark, offering insights into the military and trading history of the American West.