Fort de Cavagnial (also known as Fort Cavagnolle, Fort Cavagnal, Post of the Missouri, or Fort de la Trinité) was a French fort and trading post located on the west cliffs of the Missouri River, somewhere north of Kansas City, Kansas, and Fort Leavenworth, Kansas, from 1744 until about 1764. While the ruins of the site were still visible when Meriwether Lewis and William Clark ventured in the area during their famed 1804 westward expedition, all traces of the fort were eventually lost by the mid-19th century. Today, the exact location of the fort is a mystery.