Rising nearly 2,000 feet above the surrounding plains and visible for miles in all directions, the Sugarloaf Mountains are an isolated pair of high, conjoined ridges straddling the border between Arkansas and Oklahoma south of Fort Smith. They represent an isolated portion of the Scattered High Ridges and Mountains ecoregion of the Arkansas Valley, and the area historically supported large areas of prairie, savanna, and open woodland habitat. The ridges are part of the Cross Timbers Ecosystem, a complex mosaic of upland forest, savanna, and glade that form the broad transition zone between the eastern deciduous forests and the grasslands of the southern Great Plains. The summit of East Midland Peak (locally sometimes called Sugarloaf Mountain) is host to the largest known population of the globally rare maple-leaf oak (Quercus acerifolia). Three other species of conservation concern are known from the area: Ouachita indigo bush (Amorpha ouachitensis), Church's wild rye (Elymus churchii), and Long-bract spiderwort (Tradescantia bracteata).