The Ozarks, also referred to as the Ozark Mountains, Ozarks Mountain Country, and the Ozark Plateau, is a physiographic and geologic highland region of the central United States. It covers much of the southern half of Missouri and an extensive portion of northwestern and north central Arkansas. The region also extends westward into northeastern Oklahoma and extreme southeastern Kansas. The Shawnee Hills of southwest Illinois, which lie near the eastern edge of this region, are commonly called the "Illinois Ozarks" but are generally not considered part of the true Ozarks.