More Information on the Three Flags Ceremony:

An official transfer ceremony of the Louisiana Territory from Spain to France to the United States was held in New Orleans on November 29, 1803. A similar ceremony was held in St. Louis on March 9, 1804, when Capt. Amos Stoddard and other American officers rowed across the river from Cahokia in the Illinois Territory. Stoddard, a U.S. Artillery officer, received the territory for France, as the Spanish flag came down and the French flag went up the flagpole. Another American officer, Capt. Meriwether Lewis, delivered the territory for Spain, along with the Spanish Lieutenant Governor, Charles Dehault Delassus. The following day, March 10, 1804, the French flag came down and the stars and stripes went up the pole.

Within a very short space of time, large numbers of American emigrants moved into the Louisiana Territory, quickly outnumbering the original French inhabitants. They were followed over the next eight decades by explorers, mountainmen, pioneers in covered wagons, soldiers, buffalo hunters, railroaders, cattlemen and sodbusters, most passing through St. Louis, and some deciding to stay. The invention of the steamboat made St. Louis an essential port city, centrally located on America's greatest inland waterway. American laws, so different than the Roman law under which St. Louis had been administered under Spanish rule, changed every aspect of life in the little community. Although the fur trade remained a thriving business, the sleepy little French town would never again be the same. The colonial culture described in this portion of the Lewis and Clark website had all but disappeared by 1830.