William Clark was appointed Governor of the Missouri Territory and Superintendent of Indian Affairs for Missouri by President James Madison in 1813. As a result of his prosperity in the fur trade and his station as territorial governor, Clark was able to purchase a plot of land in April 1816 at 101-103 Main Street in St. Louis, at the corner of Vine Street. This property is now on the grounds of the Gateway Arch, near the spot where a grassy area called the "north triangle" is located. Millions of visitors pass this area each year as they walk from the Parking Garage to the Arch.

Between 1816 and 1818, Clark had a large, two story house constructed on his property, which in its day was hailed as one of the finest houses in St. Louis. Behind this mansion was a small, two-room cottage which later belonged to the explorer's son, Meriwether Lewis Clark. Next to the house, Clark added a low building made of brick, 100 feet long and 30 feet wide, which housed an Indian council chamber and a museum. Museums were not common attractions in early 19th century America. The most famous museums in the country were then located in Charleston (South Carolina), Boston, and Philadelphia, where Charles Willson Peale ran the most prestigious of all. Many of the plants, animals, and Indian artifacts collected on the Lewis and Clark Expedition were displayed in Peale's museum. Apparently Gov. Clark saved some of the artifacts from the expedition as well, and continued to collect items from American Indian visitors he received in St. Louis. These were the items which were put on display in his museum in 1816.

William C. Preston, the 21-year-old son of a prestigious Virginia family, visited the museum in 1816, and left the earliest account we have of its appearance. "On the day of the solemn diplomatic session the Governor's large council chamber was adorned with a profuse and almost gorgeous display of ornamented and painted buffalo robes, numerous strings of wampum, every variety of work of porcupine quills, skins, claws, horns, and bird skins, numerous and large calumets, arms of all sorts, saddles, bridles, spears, powder horns, plumes, red blankets and flags... In the center of the hall was a large long table, at one end of which sat the governor with a sword lying before him, and a large pipe in his hand. He wore the military hat and the regimentals of the army." Several other descriptions of the museum survive. Henry Rowe Schoolcraft, who visited in 1818, noted the "skins of remarkable animals, minerals, fossil-bones, and other rare and interesting specimens" in addition to American Indian items.

In 1821, after losing the race for Governor of the new State of Missouri, Clark was appointed Superintendent of Indian Affairs at St. Louis by President Monroe. This newly-created position made Clark the representative for U.S. Government negotiations and provisions for all Indian nations north and west of St. Louis. In addition to the prestige and importance of this position came expanded opportunities to collect Indian artifacts.

Clark's Indian Museum was open to "any person of respectability at any time," according to the St. Louis Directory of 1821. Many Easterners used a tour of the museum as their introduction to the wild west beyond. All Western travelers stopped there, because those proceeding further west moved into Indian territory - and needed to obtain a pass to do so from Clark. Famous visitors to the museum included the Marquis de Lafayette, Prince von Wurttemberg, George Catlin, William Drummond Stewart, Prince Maximilian of Weid-Neuweid, Karl Bodmer, and the Sac chief Keokuk. Perhaps the most detailed description of Clark's Museum was penned by Bernhard, Duke of Saxe-Weimar-Eisenach, who saw the collection in 1826. He was guided through the museum by Gen. Clark's secretary, Mr. Alexander, who showed him "articles of Indian clothing of different kinds, and various materials... Besides, several weapons of different tribes, wooden tomahawks, or battle-axes, in one of them a sharp piece of iron to strike into the skulls of their prisoners; another made of elks-horn, bows of elks-horn and of wood, spears, quivers with arrows, a spear head of an Indian of the Columbia river... Mr. Alexander showed us the medals which the Indian chiefs have received at different periods from the Spanish, English and American governments, and the portraits of the various chiefs who have been at St. Louis to conclude treaties with the governor, who is also Indian agent."

George Catlin first visited the museum in 1830, and was inspired to collect Indian artifacts on his western travels. Gen. Clark fully supported the efforts of the young artist to chronicle vanishing Indian lifeways and cultures. Prince Maximilian, who passed through St. Louis in 1833, left an account in his Travels which provides a glimpse of the museum in use as an Indian council chamber. He noted that "General Clarke, with his secretary, was seated opposite to the Indians, who sat in rows along the walls of the apartment. We strangers sat at the General's side, and near him stood an interpreter, a French Canadian. The Indians, about thirty in number, had done their best to ornament and paint themselves; they all looked very serious and solemn, and their chief sat at their right hand.... This conference lasted above half an hour."

At some point, probably near the end of his life, William Clark made a list of the items in his museum, which survives today at the Missouri Historical Society. The great majority of the 201 items cataloged were Indian artifacts, representing the Cherokee, Chippewa, Choctaw, Delaware, Menominee, Sauk, Shawnee, Winnebago, Arikara, Assiniboine, Comanche, Hidatsa, Iowa, Mandan, Pawnee, Ponca, Osage, Oto, and Taos nations. The most common artifacts were 45 pipe stems of Indian ceremonial pipes. A large amount of clothing was also displayed, including 18 pairs of moccasins, 11 men's suits (shirts and leggings), 2 women's dresses, necklaces, belts and garters. Weapons included ten Indian war clubs, 6 bows, 3 bow covers, 3 quivers with arrows, 3 shot pouches, a spear, a knife, and two scabbards. An entire Sioux tipi was also listed, which was painted with a "History of a battle between the Sioux & Pawnees & the Socks Fox."

No one knows what became of all these artifacts. Clark family tradition holds that a scoundrel named Albert Koch, who ran another St. Louis museum in the early 1830s at the corner of 4th and Market Streets, asked for the loan of items from the Clark Museum for use in his own museum, then absconded with them to Europe. Another version of the tale states that Clark gave Koch permission to take the artifacts to Europe in 1832. Whatever happened, by the time of Clark's death in 1838 the museum building was empty. It has been theorized by ethnologist John C. Ewers that a portion of Clark's collection is preserved in Bern, Switzerland, and survives to this day.

The history of Clark's Museum did not end with the demise of the Clark collection, however. Dr. William Beaumont rented the empty museum building from Gen. Clark in May 1838, and used it as a temporary home. Dr. Beaumont was a U.S. military surgeon whose experiments resulted in the first scientific understanding of the process of human digestion. During that same spring of 1838, a young army lieutenant named Robert E. Lee was in town with his family. Needing quarters, the Lee family rented the two-room cottage at the rear of the Clark mansion. Lt. Lee was in St. Louis on official army business. A trained engineer, he was expected to prevent the continued silting of the harbor of St. Louis. Lee's efforts literally saved the commercial life of the city. Amazingly, for one month in 1838, three world-renowned figures lived on the same block in St. Louis: William Clark, William Beaumont, and Robert E. Lee.

Gen. Clark died on September 1, 1838 in the home of his son Meriwether Lewis Clark on Broadway in St. Louis. His mansion house and the museum building were torn down in 1851 and replaced by the Union Buildings, warehouses four stories tall which, in the wake of the great fire of 1849, were described as being "fireproof throughout," according to the Missouri Republican of January 17, 1851, "even to the window frames, which will be of iron."

Despite the disappearance of these important structures over 150 years ago, William Clark's legacy lives on in St. Louis. Today, the Museum of Westward Expansion beneath the Gateway Arch continues in the same tradition as Gen. Clark's museum, displaying some similar artifacts and interpreting the American Indians of the trans-Mississippi west. A full-size Sioux tipi, reproductions of the art work of George Catlin and Karl Bodmer, and even American Indian peace medals are on display in the museum, as they were in Clark's time. A life size animatronic figure of Gen. Clark recalls the time period during which he was revered as "the red-headed Chief" and inspired many western travelers through the marvelous collection of artifacts he gathered in his "museum and council chamber" on the St. Louis riverfront.