The real find, however, is in the Ouachita Mountians, one of our oldest mountain cores, south of I-40 between Hot Springs, Arkansas and Talahina, Oklahoma. Anything north of I-40, west of US-65 is worth visiting on into the eastern fringe of the Ozarks in Oklahoma, east of US-59. It is all interesting, but I've traversed the Ozark Plateau hundreds of times over the past 35 years, gone through the Ozark Mountains only a few dozen times, on a half dozen different routes. The southern half of Missouri (south of I-70) enjoys valleys cut into the Ozark Plateau. The Ozark Mountains are in northwest Arkansas.