The United States acquired this territory and large areas west of the Mississippi River from France in the Louisiana Purchase (1803). Soon after, the government sent the Pike Expedition (1806) to explore the areas along the Arkansas River. The US founded Fort Smith in 1817 as a military post. It was named after General Thomas Adams Smith (1781–1844), who commanded the United States Army Rifle Regiment in 1817, headquartered near St. Louis. General Smith had ordered Army topographical engineer Stephen H. Long (1784–1864) to find a suitable site on the Arkansas River for a fort. General Smith never visited this town or the forts that bore his name.