Prior to the arrival of FranceFrench explorers in 1673 the area that would become St. Louis was a major center of the Mississippian cultureMississippian Mound Buildersmound builders. The presence of numerous mounds, now almost all destroyed, earned the later city the nickname of "Mound City." European exploration of the area had begun nearly a century before the city was founded. Louis Joliet and Jacques Marquette, both French, traveled through the Mississippi River valley in 1673, and five years later, René Robert Cavelier, Sieur de La SalleLa Salle claimed the entire valley for France. He called it "Louisiana" after King Louis XIV of FranceLouis XIV; the French also called their region "Illinois Country." In 1699, a settlement was established across the river from what is now St. Louis, at Cahokia, IllinoisCahokia. Other early settlements were downriver at Kaskaskia, IllinoisKaskaskia, Prairie du Pont, Fort de Chartres, and Sainte Genevieve, MissouriSainte Genevieve. In 1703, Catholic priests established a small mission at what is now St. Louis. The mission was later moved across the Mississippi, but the small river at the site (now a drainage channel near the southern boundary of the City of St. Louis) still bears the name "River Des Peres" (River of the Fathers). In 1763, Pierre Laclède, his 13-year-old "stepson" René Auguste ChouteauAuguste Chouteau, and a small band of men traveled up the Mississippi from New Orleans. In November, they landed a few miles downstream of the river's confluence with the Missouri River at a site where wooded limestone bluffs rose 40 feet above the river. The men returned to Fort de Chartres for the winter, but in February, Laclede sent Chouteau and 30 men to begin construction. The settlement was established on February 15, 1764. The settlement began to grow quickly after word arrived that the 1763 Treaty of Paris (1763)Treaty of Paris had given England all the land east of the Mississippi. Frenchmen who had settled to the river's east moved across the water to "Laclede's Village." Other early settlements were established nearby at Saint Charles, MissouriSaint Charles, Carondelet (now a part of the city of St. Louis), Fleurissant (renamed Saint Ferdinand under the Spaniards and now Florissant), and Portage Des Sioux, MissouriPortage des Sioux. In 1765, St. Louis was made the capital of Upper Louisiana. of Saint Louis, a bronze statue of the city's namesake on horseback, was widely used as a symbol of the city before construction of the Arch. From 1766 to 1768, St. Louis was governed by the French lieutenant governor, Louis Saint Ange de Bellerive, who was not appointed by French or Spanish authorities, but by the leading residents of St. Louis. After 1768, St. Louis was governed by a List of commandants of the Illinois Countryseries of governors appointed by Spanish authorities, whose administration continued even after Louisiana was secretly returned to France in 1800 by the Third Treaty of San IldefonsoTreaty of San Ildefonso. The town's population was then about a thousand. During the period when commandants appointed by Spanish authorities governed St. Louis, meetings of leading residents were also held from time to time, and "syndics" were sometimes elected to carry out certain governmental tasks. St. Louis was acquired from France by the United States under President of the United StatesPresident Thomas Jefferson in 1803, as part of the Louisiana Purchase. The transfer of power from Spain was made official in a ceremony called "Three Flags Day." On March 8 1804, the Spanish flag was lowered and the French one raised. On March 10, the French flag was replaced by the United States flag. French continued, along with English, to be one of the major spoken and written languages in St. Louis until the 1820s. St. Louis first became legally incorporated as a town on November 9, 1809, though it elected its first municipal legislators (called trustees) in 1808. The Lewis and Clark Expedition left the St. Louis area in May 1804, reached the Pacific Ocean in the summer of 1805, and returned on 23 September 1806. Both Lewis and Clark lived in St. Louis after the expedition. Many other explorers, settlers, and trappers (such as Ashley's Hundred) would later take a similar route to the West. Missouri became a state in 1820. St. Louis was incorporated as a city on December 9 1822. A U.S. arsenal was constructed at St. Louis in 1827. The steamboat era began in St. Louis on July 27 1817, with the arrival of the Zebulon M. Pike. Rapids north of the city made St. Louis the northernmost navigable port for many large boats, and Pike and her sisters soon transformed St. Louis into a bustling boom town, commercial center, and inland port. By the 1850s, St. Louis had become the largest U.S. city west of Pittsburgh, and the second-largest port in the country, with a commercial tonnage exceeded only by New York. Immigrants flooded into St. Louis after 1840, particularly from Germany, Bohemia, Italy and Ireland, the latter driven by an Old World Irish Potato Famine (1845-1849)potato famine. The population of St. Louis grew from fewer than 20,000 in 1840, to 77,860 in 1850, to just over 160,000 by 1860. Two disasters occurred in 1849: a cholera epidemic killed nearly one-tenth of the population, and a St. Louis Fire (1849)fire destroyed numerous steamboats and a large portion of the city. These disasters led to political action: old cemeteries were removed to the outskirts of the town; sinkholes were filled and swamps drained; water and sewer public utilities started; and a new building code required structures to be built of stone or brick. In the first half of the 19th century, a second channel developed in the Mississippi River at St. Louis. An island ("Bloody Island") formed between the two channels, and a smaller island ("Duncan's Island") developed below St. Louis. It was feared that the levee at St. Louis might be left high and dry, and federal assistance was sought and obtained. Under the supervision of Robert E. Lee, levees were constructed on the Illinois side to direct water toward the Missouri side and eliminate the second channel. Bloody Island was joined to the land on the Illinois side, and Duncan's Island was washed away. Militarily, the American Civil WarCivil War (1861-1865) barely touched St. Louis; the area saw only a few skirmishes in which Union (American Civil War)Union forces prevailed. But the war shut down trade with the South, devastating the city's economy. Missouri was nominally a slave state, but its economy did not depend on slavery, and it never secessionseceded from the Union. The arsenal at St. Louis was used during the war to construct ironclad ships for the Union. 1874 Eads Bridge was completed, the first road and rail bridge to cross the Mississippi River. On July 4, 1876 the City of St. Louis voted to urban secessionsecede from St. Louis County, MissouriSt. Louis County and become an independent city. At that time the County was primarily rural and sparsely populated, and the fast-growing City did not want to spend their tax dollars on infrastructure and services for the inefficient county. The move also allowed some in St. Louis government to increase their political power. This decision would later come back to haunt the City of St. Louis, the negative results of which are still visible today. Source: http://en.wikipedia.org/wiki/St._Louis%2C_Missouri