Jefferson Barracks Military Post  The Jefferson Barracks Military Post is located on the Mississippi River at Lemay, Missouri, south of St. Louis. It was an important and active U.S. Army installation from 1826 through 1946. It is the oldest operating U.S. military installation west of the Mississippi River, and it is now used as a base for the Army and Air National Guard. A Veterans Affairs healthcare system campus is located on the southern portion of the base and is also the headquarters for the Veterans Canteen Service. In 1826 General Edmund P. Gaines (Commander of the Western Department of the Army), Brig. General Henry Atkinson (commanding officer of the sixth infantry regiment), explorer William Clark, and Missouri Governor John Miller spent several days searching the banks of the Mississippi River for the perfect location for a new post to replace Fort Bellefontaine. A site near the city of "Vide Poche" or Carondelet, ten miles (16 km) south of St. Louis, was recommended and then approved by Major General Jacob J. Brown, Commanding General of the Army. On July 10, 1826, two days after the deed to the land was signed, the first military troops—six officers and 245 enlisted men of Companies A, B, H and I of the 1st Infantry Regiment, commanded by Brevet Major Stephen Watts Kearny—arrived at the new post and started building temporary quarters that they named Cantonment Miller in honor of Governor Miller. In 1827 the military post was formally named Jefferson Barracks in honor of Thomas Jefferson who had died the year before. Even William Clark's son, Meriwether Lewis Clark, Sr., would join the ranks of Jefferson Barracks. It was also designated the first "Infantry School of Practice." The first conflict that the men of Jefferson Barracks were involved with was the Black Hawk War in 1832. Troops were deployed from Jefferson Barracks to push "hostile Indians" back into their village in present-day Iowa. Chief Black Hawk was captured and brought back to Jefferson Barracks. In 1832, the United States Regiment of Dragoons were formed and stationed at Jefferson Baracks. The dragoons, trained to fight mounted or dismounted, were the first unit of permanent cavalry in the United States Army and were later called the 1st U.S. Dragoons. Jefferson Barracks became a major military post during the Mexican–American War (1846–1848) when it served as a rest and supply station for most U.S. troops deploying to Mexico.