Because 24 percent of Oklahoma’s topography—nearly 10 million acres—is forest, the state ranks ninth in the nation for timber production. The largest sawmill east of the Rocky Mountains is located in Oklahoma. In the Ouachita Mountains and the Ozark Plateau in the eastern part of the state, hardwoods predominate. In the mountainous southeast, the forests are dense with pine and oak trees. Through central Oklahoma, post oak and blackjack oak dot the tallgrass prairies, pastures, and croplands. In the southwest, oak shinnery and mesquite spread onto rangeland. Oklahoma has 144 native species of trees including pecan, walnut, pine, several types of oak, and cottonwood. In the fall, the sugar maple and Caddo maple of Caddo County are no less colorful than the maples of New England. Fall color is most prominent in the Ouachita National Forest of southeast Oklahoma.