Its southern extremity, the "Llano Country", as it is called, has a granite foundation, much quarried, and deposits of hematite and magnetite occur here plentifully.
On the eastern side the soils show a carboniferous area, and include sands, loams, black and light-coloured clays, producing in the heavier soils, cotton, wheat, oats, sorghum, milo-maize, and in the lighter, cotton, maize, fruit, and garden products.
Extending back from the Gulf Coast for from thirty to fifty miles, an outcrop of underlying clays gives a flat, almost treeless tract running along the whole length of the coast and known as the Coast Prairie.
The first of these, nearest the coast, is called the Coastal Plain, consisting of Coast Prairies, a Tertiary area, and Black Prairies.
On the west and south-west boundary the Rio Grande runs for 1200 miles.
In the arid regions the drainage channels flow only for a short time after rainfall.
This Tertiary area also is divided by climatic conditions.
The south- western and western part, the "Rio Grande Plain", having a very shallow rainfall, produces only a dwarfed and shrubby natural vegetation and is hence called the "Chaparral Country"; the humid part, however, north and north-east, called the East Texas timber belt, grows both the short and long-leaf pine. In the northern part of this region more fertile soil affords the great fruit and "truck" products; cotton and tobacco are also grown.
The name, Texas, is probably derived from Tejas, the name of a friendly tribe of Indians met within the territory by the early Spanish explorers. Irrigation, however, in this south-western region makes the cultivation of sugar-cane and sorghum as well as cotton of some profit.
The state is bounded on the north by Oklahoma, on the west by New Mexico and Mexico, on the south by Mexico and the Gulf of Mexico, and on the east by the Gulf of Mexico, Louisiana, and Arkansas. Favourable underground conditions make this Coast Prairie the location of important oil-fields.