The Piney Woos is a terrestrial ecoregion in the Southern United States covering 54,400 mi² (140,900 km²) of East Texas, Southern Arkansas, Western Louisiana, and Southeastern Oklahoma. This coniferous forest, is dominated by several species of pine, including Longleaf Pine, Shortleaf Pine and Loblolly Pine, as well as several varieties of hardwoods including Hickory and Oak. The World Wide Fund for Nature considers the Piney Woods to be one of the critically endangered ecoregions of the United States.