Throughout the pre–Civil War period and during the war, Missourians were sharply divided in their opinions about slavery and in their allegiances, supplying both Union and Confederate forces with troops. However, the state itself remained in the Union.
Historically, Missouri played a leading role as a gateway to the West, St. Joseph being the eastern starting point of the Pony Express, while the much-traveled Santa Fe eastern terminus was Franklin in 1921, Missouri; by 1832, Independence, Missouri; and by 1845, Kansas City, Missouri. Independence, Missouri was the most popular "jumping off" point on the Oregon Trail.
Missouri's recorded history begins in the latter half of the 17th century when the French explorers Jacques Marquette and Louis Jolliet were the first white people to see the Missouri River in 1673, followed by Robert Cavelier, sieur de La Salle, who in 1682 claimed the whole area drained by the Mississippi River for France, calling the territory Louisiana , after King Louis XIV.
When the French explorers arrived the area was inhabited by Native Americans of the Osage and the Missouri groups, and by the end of the 17th century French trade with the Native Americans flourished.
In the early 18th century the French worked the area's lead mines and made numerous trips through Missouri in search of furs. Missionaries established St. Francis Xavier, the first white settlement of Missouri. It was located near present-day St. Louis, but was deserted in 1703. Trade down the Mississippi prompted the settlement of Ste. Geneviève about 1735 and the founding of St. Louis in 1764 by Pierre Laclede and René Auguste Chouteau, who were both in the fur-trading business.
Although not involved in the last conflict (1754–63) of the French and Indian Wars, Missouri was affected by the French defeat when, in 1762, France secretly ceded the territory west of the Mississippi to Spain. Although few Spaniards settled Missouri, many U.S. miners and farmers entered from Mississippi.
In 1800, France reclaimed the Louisiana Territory and in 1803, sold it to the United States as part of the Louisiana Purchase. French influence remained dominant, even though by this time Americans had filtered into the territory, particularly to the lead mines at Ste Geneviève and Potosi. By the time of the Lewis and Clark expedition (1803–6), St. Louis was already known as the gateway to the Far West.
The Missouri Territory was organized in 1812., but settlement was slow even after the War of 1812. The coming of the steamboat increased traffic and trade on the Mississippi, and settlement progressed. Planters from the South had introduced slavery into the territory, but their plantations were restricted to a small area.
As people flooded into Missouri, Native Americans grew angry and began raiding settlements. During the War of 1812, Britain supplied the Indians with weapons and encouraged them to attack Missouri settlements. Not until 1815 did the attacks end with a peace treaty at Portage des Sioux. By 1825, few Native Americans lived in Missouri.
However, the question of admitting the Missouri Territory as a state became a burning national issue because it involved the question of extending slavery into the territories. Attempts for statehood started in 1818, but questions concerning slavery in the state were not settled until 1820. The dispute was resolved by the Missouri Compromise, which admitted (1821) Missouri to the Union as a slave state but excluded slavery from lands of the Louisiana Purchase north of lat. 36°30´N. (All of Missouri lies north of 36°30´ except for the southeastern "bootheel") and allowed Maine become a free state. This kept the number of slave and free states equal. Missouri became the 24th state on Aug. 10, 1821.
Slaveholding interests became politically powerful, but the state remained principally a fur-trading center. The American Fur Company organized in St. Louis in 1822 and soon developed a monopoly on all fur trade west of the Mississippi River. Trade with Mexico was very successful. The Santa Fe Trail connected Independence with the Southwest. Independence also marked the beginning of the Oregon Trail that led thousands to the Pacific Northwest.
In 1854 the problem of slavery was made acute with the passage of the Kansas-Nebraska Act, leaving the question of slavery in the Kansas and Nebraska territories to the settlers themselves. The proslavery forces in Missouri became very active in trying to win Kansas for the slave cause and contributed to the violence and disorder that tore the territory apart in the years just prior to the Civil War. Nevertheless Missouri also had leaders opposed to slavery, including one of its Senators, Thomas Hart Benton.
In 1857, the U.S. Supreme Court ruled in the Dred Scott Decision that slaves were considered property. This historic decision increased tension between the North and the South. Kansas, located on Missouri's western border, became a free state in 1861. Fighting between Kansas and Missouri began and continued into the Civil War.
During the Civil War most Missourians remained loyal to the federal government. In 1861, a convention was called to determine whether Missouri would secede from the Union. Although the majority voted to support the Union, Governor Claiborne Jackson refused to send troops at the request of President Lincoln. Jackson led the state militia against Union troops at the Battle of Boonville. Jackson's militia was forced to southern Missouri where they defeated Union troops at Wilson' Creek. Shortly after, the state convention met again to remove all pro-Confederate state leaders from office.
The coming of the railroads brought the eventual decay of many of Missouri's river towns and tied the state more closely to the East and North. St. Louis and Kansas City became important railroad centers. Outlaws held up banks, stagecoaches, and trains. Jesse James terrorized the state for over 20 years until he was killed by one of his own gang in 1882. Urbanization and industrialization progressed, and the Louisiana Purchase Exposition, held at St. Louis in 1904, dramatically revealed Missouri's economic growth. The following year laws were passed that required inspection of working conditions and regulation of child labor and public utilities in Missouri.
Although during World War I, general prosperity prevailed in the state. Missouri's industries expanded to help supply war materials. John Pershing of Linn County was named commander in chief of the U.S. forces in France. The Great Depression (1929-1939) caused more than 200,000 Missourians to lose their jobs and some to lose their land. The federal government established programs to help bring employment to Missouri.
World War II (1939-1945) also revived the economy as factories again opened to provide war materials and both St. Louis and Kansas City served as vital transportation centers, and industrialization increased enormously. In the postwar period, Missouri became the second largest producer (behind Michigan) of automobiles in the nation. Although most industry remains based in the two metropolitan centers, smaller Missouri communities, especially suburbs, have since attracted much light and heavy industry, as well as former city dwellers. St. Louis lost half its population between 1950 to 1990, and out-migration has continued; what was once the fourth largest U.S. city is now barely in the top 50 in size.
New industries moved to Missouri during the 1950s. A uranium-processing plant opened in Weldon Spring, electronic plants were built in Joplin, and factories in St. Louis and Neosho began producing parts for spacecrafts. Economic growth continued through the 1960s. State leaders encouraged tourism and the expansion of mining throughout the state.
Missouri encountered serious pollution problems in the early 1980s. Contamination threatened ground water supplies and poisonous substances were discovered in Times Beach. The federal government is striving to help Missouri clean these areas. As urban problems became serious, St. Louis and Kansas City rebuilt their riverfronts. Missouri was also faced with financial problems. In 1986, a state lottery was established to help with education, welfare, and environmental programs.
Today in spite of these difficulties, Missouri continues to grow and the economy remains strong.