The Cross Timbers are two long, narrow strips of timber extending parallel to each other from Oklahoma to Central Texas, forming a marked contrast to the adjacent prairie. The more fertile East Cross Timbers begin here in Cooke County. The area was a famous pioneer landmark as well as an obstacle to travel because of its dense growth. It divided the hunting grounds of the Plains and East Texas Indians. Until the 1870s it marked the boundary of settlement, for Plains Indians avoided the timber. The forests' most important function was, and is, causing soil to retain water.