Some more background info.

United State Rifle Model 1841 - Commonly referred to as the “Mississippi Rifle,” the Model 1841 rifle is regarded by many weapons experts as one of the most handsome of all percussion cap system firearms. The .54 caliber “Mississippi Rifle” owes its nickname to the successful use of this weapon by a Mississippi regiment under the command of Jefferson Davis in the Mexican War. During its period of manufacture and use, military authorities regarded the Model 1841 as the best of its type. The Harpers Ferry Armoury manufactured a total of 25,296 of these rifles and contractors produced another 45,500. The walnut stock held a 33-inch round barrel which was fastened by two barrel bands. Brass mountings were finished bright while the barrel remained brown. The lock plate was casehardened, and the Model 1841, as with most rifles of this time period, had a large patch box located on the right side of the stock. Initially, the rifle was not fitted with a bayonet. However, beginning in 1855, the Model 1841 rifle was remanufactured to support a sword bayonet that was developed with three different fittings stud, ring, and socket. Just prior to the Civil War, 8,879 of these weapons were rebored to .58 caliber, improved rear sights were added, and their brass tipped ramrods were replaced by an all steel type with an exaggerated trumpet head profile.

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Type two bayonet for the Model 1841 rifle.

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David

Lewis and Clark was much earlier.

The Lewis and Clark Expedition, also known as the Corps of Discovery Expedition, was the first American expedition to cross what is now the western portion of the United States, departing in May, 1804 from St. Louis on the Mississippi River, making their way westward through the continental divide to the Pacific coast.
The expedition was commissioned by President Thomas Jefferson shortly after the Louisiana Purchase in 1803, consisting of a select group of U.S. Army volunteers under the command of Captain Meriwether Lewis and his close friend Second Lieutenant William Clark. Their perilous journey lasted from May 1804 to September 1806.

David