OKLAHOMA is a west south central State of the United States of America, lying between 35' and 37° N. lat. and 29' and 103° W. long. It is bounded north by Colorado and Kansas; east by Missouri and Arkansas; south by Texas, from which it is separated in part by the Red river; and west by Texas and New Mexico. It has a total area of 70,057 sq.m., of which 643 sq.m. are water-surface. Although the extreme western limit of the State is the Io3rd meridian, the only portion W. of the ooth meridian is a strip of land about 35 m. wide in the present Beaver, Texas and Cimarron counties, and formerly designated as "No Man's Land." Oklahoma is called the "Sooner State" because those who entered on April 22, 1889, with the rush, found much of the best land taken up by those who had evaded the guards and entered the territory in advance of the official open ing. These persons who evaded the regulations and thus secured the best land were known as "Sooners." Physical Features.—The topographical features of the State exhibit considerable diversity, ranging from wide treeless plains in the west to rugged and heavily-wooded mountains in the east. Elevations above the sea range from 4,800 ft. (Black Mesa) in the extreme north-west to 30o ft. in McCurtain county in the south-east. The State has a mean elevation of 1,300 ft., with sq.m. below f,000 ft.; 25,400 sq.m. between i,000 and 2,000 ft.; 6,500 sq.m. between 2,000 and 3,00o ft.; and 3,600 sq.m. between 3,00o and 5,000 feet.
this plateau lie the Wichita mountains, a straggling range of rugged peaks rising about 1,5oo ft. above the plain, but on account of their steep and rugged slopes they are difficult to ascend. A third group of hills, the Chautauqua mountains, lie in the west in Blaine and Canadian counties, their main axis being almost parallel with the North Fork. The north-western part of Oklahoma is a lofty table-land forming part of the Great Plains region east of the Rocky mountains.
The prairies north of the Arkansas and west of the Neosho rivers are deeply carved by small streams, and in the western portion of this area, where the formation consists of alternating shales and sandstones, the easily eroded rocks have been carved into canyons, buttes and mesas. South of the Arkansas river these ledges of sandstone continue as far as Okmulgee, but the evi dences of erosion are less noticeable. East of the Neosho river the prairies merge into a hilly woodland. In the north-west four salt plains form a striking physical feature. Of these, the most noted is the Big Salt plain of the Cimarron river, in Woodward county, which varies in width from 1- m. to 2 m. and extends along the river for 8 miles. The plain is almost perfectly level.
Following the slope of the land, the important streams flow from north-west to south-east. The Arkansas river enters the State from the north near the 97th meridian, and after following a general south-easterly course, leaves it near the centre of the eastern boundary. Its tributaries from the north and east—the Verdigris, Grand or Neosho and Illinois—are small and unim portant; but from the south and west it receives the waters of much larger streams—the Salt Fork, Cimarron and the Canadian, with its numerous tributaries. The extreme southern portion of the State is drained by the Red river, which forms the greater part of the southern boundary, and by its tributaries, the North Fork, the Washita and the Kiamichi.