Physical Geography

Missouri is divided among three major physical regions of the United States: the Ozark Plateau, or Ozarks; the Central Lowlands; and the Gulf Coastal Plain.

The Ozark Plateau. Most of the southern half of the state is in this region. It is an eroded tableland, consisting mainly of rolling hills and deep river valleys often lined by bluffs. The highest section is the St. Francois Mountains in the southeast. Here, amid igneous rocks that are among the oldest in the nation, stands Taum Sauk Mountain, at 1,772 feet (540 m) the highest point in the state. The plateau is honeycombed with caves, underground water channels, and sink holes—typical features of karst topography.

The Central Lowlands. Northern and western Missouri lie in this region. The northern part, stretching from Iowa to the Missouri River, consists mainly of flat to rolling prairies. Laid down by glaciers early in the Ice Age, they are more eroded and rougher than the younger prairies of the Midwest. Western Missouri, from the Missouri River southward to Joplin, is a rolling unglaciated plains region that resembles the Great Plains farther west.

The Gulf Coastal Plain, usually called the Bootheel, is in the southeastern corner of the state. Flat, low-lying, and occasionally marshy, it is part of the Mississippi River's flood plain. The region was formed millions of years ago by sediments in the Mississippi's first delta. Located here is the lowest point in the state, 230 feet (70 m) above sea level.

Missouri's rivers vary from clear, sparkling streams in the Ozarks to such muddy giants as the Missouri and the Mississippi. The Mississippi River, flowing southward to the Gulf of Mexico, receives the Des Moines, Salt, and Meramec rivers. Near St. Louis, the Mississippi is joined by the Missouri River, which forms part of the western boundary and drains eastward across the state from Kansas City. Tributaries of the Missouri include the Platte, Grand, and Chariton from the north, and the Osage and Gasconade from the south. Other rivers include the Current, Black, and St. Francis, which flow southward into Arkansas.

Lake of the Ozarks and adjoining Harry S. Truman Reservoir are the largest lakes in the state. Both are on the Osage River in west-central Missouri. Lake of the Ozarks is the center of a major resort area. Lake Taneycomo, a relatively small reservoir near the Arkansas border, is also the center of a popular resort area. Other lakes include Table Rock, Bull Shoals, and Norfolk lakes on the Missouri-Arkansas state line; Lake Wappapello, in the southeast; and Mark Twain Lake, in the northeast.

The Ozark region is noted for its many large springs. Twelve have daily flows of 64,000,000 gallons (242,000,000 liters) or more. Big Spring, with a maximum flow of 846,000,000 gallons (3,200,000,000 liters) a day, is one of the largest single springs in the nation.

Missouri has a humid continental climate similar to that of other centrally located states. Summers are long and vary from warm to hot; winters are relatively short and cold. A chief mark of the climate is its highly changeable weather.

July temperatures average 78° to 80° F. (26° to 27° C.); January temperatures 26° to 36° F. (-3° to 2° C.), the warmest area being the Bootheel. Summer temperatures often rise to more than 90° F. (32° C.) but rarely reach 100° F. (38° C.). Winter temperatures seldom fall below 0° F. (-18° C.).

The state receives roughly 35 to 50 inches (890 to 1,270 mm) of precipitation each year, the increase being from northwest to southeast. Rains are often erratic, however, and droughts occasionally occur. Snowfall averages 18 to 22 inches (460 to 560 mm) in the north and about half as much in the south. Seldom is it deep or on the ground for long. Sleet storms and tornadoes occasionally strike the state.

Forests once covered most of Missouri, but now occupy only about one-third of the state. The vast majority of the present forests consist mainly of second-growth hardwoods, particularly oaks. The southern part of the state, especially the southeast, is the principal forested area. The northern part, once covered by grasslands and forests, is now used extensively for farming.