The Cross Timbers of Texas is two long and narrow strips of forest region that extend parallel to each other from Oklahoma southward to Central Texas between the ninety-sixth and ninety-ninth meridians and form a marked contrast to the prairies of the state. The Eastern (or Lower) Cross Timbers, a narrow band of blackjack and post oak, separates the region of Black Prairies on the east from the Grand Prairies on the west. The Eastern and Western Cross Timbers are formed by a narrow band of woodland extending along Red River. Toward the south the Eastern Cross Timbers belt spans the ninety-seventh meridian from the Red River to the Brazos River. Beginning in the eastern half of Cooke County, it extends southward through the eastern parts of Denton, Tarrant, and Johnson counties and the western parts of Grayson, Dallas, Ellis, and Hill counties. The average width of the Eastern Cross Timbers does not exceed fifteen miles, and its features disappear near the Brazos at Waco. The altitude of the belt is slightly higher than that of the surrounding prairies. The soil of the Eastern Cross Timbers differs from that of the Western in that the Eastern is more fertile and therefore produces larger trees and a wider variety of trees and shrubs. In pioneer times the band of timber was a famous landmark. It was also a formidable obstacle to travelers because of the density of growth. It served as a dividing line between the hunting grounds of the Plains Indians and East Texas Indians. Comanches raided east of the Cross Timbers in the early years, and the Wichitas and others used the wood in the Cross Timbers. Indians used the Cross Timbers as a north-south avenue that afforded secrecy from enemies. Cross Timbers oaks are used for firewood, railroad ties, and poles, but the most important function of the timber belt is preserving water. The timber prevents rain water from immediately running off the surface and causes much of it to soak into sand that supplies artesian water for hundreds of wells to the east and south of the Cross Timbers. The region is well adapted for truck farming. Cotton and corn are also grown.
The Western (or Upper) Cross Timbers comprises an irregularly bounded wooded region in north central Texas, extending in a generally southward direction through Montague, Wise, Jack, Parker, Hood, Erath, and Comanche counties. Topographically, much of the Western Cross Timbers is characterized by rough features, in contrast to the smooth outlines of the lands both to the east and to the west. The region at large, underlain by nonlimy geologic materials, is not easily eroded; constructional areas are few, and where they do occur, at the foot of longer slopes, they are of small extent. Since the region has a subhumid climate, its natural vegetation would ordinarily be grass; its scrubby tree growth results from edaphic features. The Western Cross Timbers is underlain by three larger groups of geologic formations: the Trinity sands of the Comanchean or Lower Cretaceous, the hard rocks of the various Pennsylvanian formations, and the Continental Red Beds materials of the Wichita formation in the Lower Permian. Owing to the fact that the parent materials are prevailingly noncalcareous, both the soils and the natural vegetation of the Western Cross Timbers areas differ sharply from soils of adjacent areas underlain by either "hard" or "soft" formations that are also highly calcareous. In fact, outcrops of the Paluxy sands are interspersed among calcareous materials to the east of the Trinity sands; without exception, the narrow belts of Paluxy sand outcrops support a growth of hardwoods, forming ribbons of woodland in an area where grasses would normally predominate. Topographic types in the region vary with the major geologic formations that outcrop in the area. The Trinity sands area at the east is a plain much of the surface of which is now so eroded as to forbid its use agriculturally. The Pennsylvanian outcrops form a plateau dissected by the channels of major streams that have been cut considerably below the surface level. The portion of the Western Cross Timbers underlain by the Wichita formation is a hilly and maturely dissected; in it the woodland vegetation is more scattered and more dwarfed than is the case in eastward-lying areas of the region. Soil and variations parallel both the topography and the geologic materials. The natural vegetation is a woodland predominantly made up of dwarfed post oaks. Short grasses occur over much of the area in localities where the woodland growth is sparse. Some of the areas underlain by deep sands support a growth of tall grasses. Among the Pennsylvanian outcrops occur scattered exposures of hard limestones; without exception, such exposures are characterized by a typical savanna landscape, comprising scattered mesquite shrubs underlain by a floor of sod-forming short grasses. The Western Cross Timbers country presents a landscape unexpected in West Texas. The region has been important chiefly for its mineral resources. Portions of the Trinity sands area are now important in peanut culture as well as for the growing of small fruits. In pioneer days the woodland growth on the Trinity sands supplied fuel for settlers on the western frontier of Texas as well as timber for log houses. The Trinity sands outcrop is an important intake area for meteoric water that forms important aquifers to the east where the formation continues in the subsurface. This was an important influence on early settlement as underground water was available from shallow wells dug into the Trinity sands. (see LOWER PLAINS.)