MISSOURI, popularly known as the "Show Me" State, occu pies a central position in a group of 17 States which comprise the great agricultural plain of the Mississippi valley. It is situ ated about goo and 1,600 m. respectively from the Atlantic and Pacific coasts and approximately midway between Canada and the Gulf of Mexico. It is bounded on the north by Iowa; east by Illinois, Kentucky and Tennessee ; south by Arkansas; and west by Oklahoma, Kansas and Nebraska. Its length from north to south, disregarding the St. Francois projection south ward, is about 285 m., the width from west to east varies from 210 to 310 m., and the total area of the State is approximately 69,42o sq.m. of which approximately 693 are water surface. The State takes its name from its great river, the Missouri, which was named after a tribe of Indians who inhabited the country near the river mouth. The highest recorded elevation in the State is Taum Sauk mountain (1,75o ft.) in Iron county, and the lowest is on the flood plain of the Mississippi river in the south-east corner of Pemiscot county (229 ft.). The approximate mean ele vation for the State is Boo feet.
Physiographic Regions.---Missouri is divided into four dis tinct physiographic regions : the old, glaciated and river plains, and the maturely dissected or Ozark highlands. The old plains region occupies about one-fifth of the area of the State, and is situated south of the Missouri river and west of the Ozark high lands. This topographic condition extends for a considerable dis tance into the adjoining States of Kansas, Oklahoma and Arkansas. It is underlain by shales, sandstones and limestones of Pennsyl vanian and Mississippian age and is a region of topographic old age.
The glaciated plains occupy the major portion of the State north of the Missouri river. This region is underlain mainly by Mis sissippian and Pennsylvanian rocks and glacial and loessal deposits. Rocks belonging to earlier Paleozoic periods occur along the Mis souri, Mississippi and other rivers. Pre-glacial features were
similar to those now present in the old plains region. Post-glacial erosion has developed a topography characterized by extremely shallow valleys along the streams, and flattish inter-stream areas. The river plains are flat areas varying in width from less than a mile to as much as 8 or IQ m. along the main streams, but in the south-eastern area the river plain is from 3o to 6o m. wide. The Ozark highland, in Missouri, is a part of a highland area of considerable extent lying in the States of Illinois, Missouri, Arkansas and Oklahoma. It is underlain by pre-Cambrian igneous rocks and by sedimentary rocks ranging from Cambrian to Penn sylvanian in age, with Cambrian and Ordovician rocks underlying most of the region. Occupying in Missouri about two-fifths of the State, the Ozark highlands are distinguished by greater elevation and a more completely dissected surface. The general shape of the highland is an elongated dome, whose longer axis extends from the vicinity of St. Francois county south-westward across the State into north-central Arkansas. In the east is an area of granite knobs, peaks and ridges covering some 7o sq.m., commonly called the St. Francois mountains, which are only from Soo to Boo ft. above the adjacent valleys. In the south-western part the surface is rougher and more elevated continuing into Arkansas. The highlands are noted for their swift, clear streams abounding in game fish.