Missouri is not geologically static. Beneath the southeastern part of the state lies the Reelfoot Rift, a scar in the earth’s crust where the continent attempted to split roughly 600 million years ago. The failed rift remains present today and contributes to seismic activity in the central United States.
Between 1811 and 1812, a series of earthquakes estimated at magnitudes between 7.5 and 8.0 struck near New Madrid. The ground shifted so abruptly that the Mississippi River temporarily flowed backward. The quakes were felt far beyond the region; the eastern half of the continent sits on older, denser rock that transmits seismic energy efficiently, and church bells rang in Boston, more than a thousand miles away. A quake of similar strength in California would likely not be felt far beyond that state’s borders.
The violent shaking also caused sandy soil in the Bootheel region to liquefy. Pressurized water and sand forced their way up through cracks, creating sand boils that buried or destroyed thousands of acres of farmland. In some areas, the ground dropped several feet in seconds, and floodwaters from the Mississippi filled the new lowlands. Reelfoot Lake, located just across the state line, formed almost overnight as a result.
The state’s geology is much older than its surface appearance suggests. The granite in Missouri’s St. Francois Mountains is between 1.4 and 1.5 billion years old, among the oldest exposed rock in North America. Elephant Rocks State Park features large pink granite boulders, some weighing more than 600 tons, shaped by erosion into forms that resemble a herd of elephants. At Hughes Mountain, ancient volcanic rhyolite cooled slowly and fractured into near-perfect hexagonal columns, similar to the Giant’s Causeway in Ireland but on a smaller scale.
Much of Missouri’s bedrock was once the floor of a shallow tropical sea. Farmers in the central part of the state sometimes find fossilized crinoids, remains of marine animals, while plowing fields. The eastern branch of the Black River at Johnson’s Shut-Ins is squeezed through narrow channels in the same 1.5-billion-year-old rhyolite, creating natural rapids.
Missouri is known as the Cave State, with more than 7,500 recorded caves, second only to Tennessee nationally. The limestone that underlies much of the southern half of the state has been hollowed out into extensive passages. SubTropolis, a 55-million-square-foot underground business complex in Kansas City, was carved into a limestone bluff and now houses warehouses, offices, and data centers. Because limestone caves maintain a naturally cool, consistent temperature, the federal government stores surplus butter and cheese in Missouri’s underground storage areas, reducing refrigeration costs.
Several parks and attractions are directly tied to the state’s cave systems. The main square of Silver Dollar City sits above Marvel Cave, whose entrance room is one of the largest cave chambers in North America. Ha Ha Tonka State Park features a 250-foot-deep canyon formed not by a river but by the collapse of a massive cave system. Grand Gulf State Park contains a 130-foot-deep gorge that also resulted from a collapsed cave roof rather than gradual erosion.
Big Spring in the Ozarks discharges an average of 278 million gallons of water per day, fed by an underground river network draining the surrounding karst limestone. The spring’s daily output is roughly equivalent to the water consumption of a mid-sized city.
Lake of the Ozarks, a reservoir formed by flooding a maze of narrow, winding valleys, has a shoreline of more than 1,150 miles. That exceeds the roughly 840 miles of California’s Pacific coastline. The Gasconade River covers about 300 miles of actual flow but advances only about 120 miles in a straight line, making it one of the most meandering rivers in the world. In the state’s limestone regions, sections of rivers sometimes disappear into sinkholes, travel underground, and resurface miles away, occasionally in a different watershed.
Missouri’s weather has also been notable. The deadliest tornado in U.S. history struck southeastern Missouri in 1925 before cutting a 219-mile path across Illinois and Indiana. In 2011, an EF5 tornado hit Joplin, becoming one of the costliest tornadoes in modern American history. The Missouri River roughly marks the southern edge of the last glacial period’s advance; land north of the river is flat, glacially formed prairie, while land south of it is the rugged, unglaciated Ozark Plateau. With no mountain ranges to block arctic air from the north or Gulf moisture from the south, temperatures in Missouri can swing by as much as 50 degrees Fahrenheit in a single day.
In 2005, a reservoir atop Proffit Mountain failed, releasing a wall of water carrying approximately 1.3 billion gallons down Taum Sauk Mountain in minutes. The flooding was contained to the surrounding area, and the reservoir was later rebuilt. During the Great Flood of 1993, the confluence of the Missouri and Mississippi rivers near St. Louis overflowed so extensively that floodwaters stretched roughly 20 miles wide in places.
The Old Lead Belt in the southeastern part of the state once supplied a significant share of global lead production. The mining operations left behind large piles of toxic waste that remain visible from miles away.
Tower Rock, a large limestone formation rising from the Mississippi River near Perryville, becomes accessible on foot when river levels drop low enough for visitors to walk across the exposed riverbed. Across the Ozarks, patches of shallow soil over bedrock create dry, desert-like conditions where cactus and scorpions can be found. The Ozark hellbender, a fully aquatic salamander reaching two feet in length, still lives in the region’s cold, spring-fed streams; it has remained largely unchanged since before the dinosaurs.
The Squaw Creek National Wildlife Refuge hosts more than one million snow geese and hundreds of bald eagles during fall migration. The Bootheel, now flat farmland, was once dense cypress swamp similar to Florida’s Everglades before large-scale drainage projects in the early twentieth century transformed it into productive agricultural land.
Missouri borders eight states, tying it with Tennessee for the most neighbors of any U.S. state. Its southern boundary is not a straight line; the Bootheel protrusion was added in 1821 after landowner John Hardeman Walker lobbied to keep his property within Missouri rather than in the adjacent territory. In 1839, Missouri and Iowa nearly came to open conflict over a disputed nine-mile strip of land. The dispute became known as the Honey War after a Missouri tax collector cut down three beehive trees owned by an Iowa farmer while enforcing contested boundary lines. The matter was eventually settled by the U.S. Supreme Court.
In 1881, a major flood shifted the course of the Mississippi River so dramatically that the Illinois town of Kaskaskia ended up on the Missouri side of the river. The town remains legally part of Illinois but is accessible by land only through Missouri. The Missouri-Kansas border was the site of violent raids during the Bleeding Kansas period in the years before the Civil War.
The state’s southern border, at latitude 36 degrees 30 minutes, became the legal dividing line between free and slave territories across the western United States under the Missouri Compromise. That boundary shaped the geography of one of the most consequential political settlements in American history.
Kansas City’s Country Club Plaza, opened in 1922, is widely regarded as the first regional shopping district designed specifically for automobile access. Before mechanical refrigeration, Missouri brewers converted natural limestone caves into large underground cellars for aging beer, using the caves’ constant year-round temperatures. The state’s highest and lowest elevations are both in the southeastern corner: Taum Sauk Mountain at 1,772 feet and the St. Francis River at 230 feet.
The Gateway Arch in St. Louis stands exactly 630 feet tall and 630 feet wide, a one-to-one ratio that makes it the tallest memorial in the world. Arrowhead Stadium in Kansas City holds the Guinness record for the loudest outdoor stadium, recording 142.2 decibels. Kansas City has more than 200 registered fountains, more than any city in the world except Rome.
Westward expansion began in western Missouri. The Santa Fe, Oregon, and California trails all had their true starting points near Independence and St. Joseph. The Pony Express also launched from St. Joseph in 1860, chosen because it was then the farthest western point connected by telegraph and railroad.
The Missouri and Mississippi rivers, the two longest in North America, meet just north of St. Louis. The town of Ste. Genevieve retains the largest concentration of French colonial architecture in North America, more than Louisiana or Quebec, a remnant of France’s original claim to the entire Mississippi Valley.
In the 1870s, the phylloxera aphid was destroying French vineyards at their roots. Missouri grapevines, which had natural immunity to the pest, were shipped across the Atlantic and grafted onto French rootstock. The practice saved the French wine industry from collapse, and nearly all French wine produced since then has grown on roots originally from Missouri.
