1673: French missionaries Father Jacques Marquette and Louis Joliet explore the central United States along the Mississippi River south to the Arkansas River.
1682: Rene-Robert Cavelier, Sieur de La Salle, reaches Missouri on his way to the mouth of the Mississippi. He visits
a Quapaw village and claims the land in the name of King Louis XIV.
1724: Frenchman Etienne de Bourgmont builds the first fort on the Missouri River
1763: Most of Louisiana (which included Missouri) becomes a Spanish possession as a result of the defeat of the French by the British in the French and Indian War.
1764: St. Louis was founded in 1764 by the Frenchman Pierre Laclède Liguest.
1800: French ruler Napoleon I re-acquires Louisiana Territory from the Spanish in the Treaty of San Ildefonso.
1803: Napoleon I offers to sell New Orleans and the entire Louisiana Territory (which included an area much larger than present-day Louisiana) to the U.S. Government for $15,000,000. The United States agrees and doubles in size.
1804: American explorers Meriwether Lewis and William Clark begin their three year exploration of the Louisiana Territory and beyond at St. Louis.
1811: The New Madrid earthquakes rock the town of New Madrid and caused permanent changes in the course of the Mississippi River. The series of earthquakes were the most powerful in recorded American history.
1812: The Missouri Territory is carved from the Louisiana Territory.
1821: As a result of the Missouri Compromise, Missouri becomes the 24th state and enters the Union as a slave state.
1846 – 1857: The Supreme Court rules that free slaves could be re-enslaved in the infamous Dred Scott Decision.
1848: Independence, Missouri becomes a popular starting out point for settlers heading west on the Santa Fe, Oregon, and California Trails, as well as for those heading to the California Gold Rush.
1861-1865: Missouri is the site of several decisive battles during the Civil War, though the slave state never secedes from the Union, classifying it as a "border state." Roving bands of Missouri guerillas known as Quantrill’s Raiders massacre hundreds of Union supporters and spread terror through Missouri, Kansas, Oklahoma, and Texas.
1965: Construction begins on the Gateway Arch in St. Louis.