High Quality Content by WIKIPEDIA articles! The American Southwest has long been occupied by hunter/gatherers and agricultural people. This area, identified with the current states of Colorado, Arizona, New Mexico, Utah, and Nevada, and areas of northern Mexico, has seen successive prehistoric cultural traditions since approximately 12,000 years ago. According to anthropologist and popular author Brian Fagan, it is likely that both ceramic and irrigation technology were indigenous developments of these cultures. Many contemporary cultural traditions exist within the American southwest, including Yuman-speaking peoples inhabiting the Colorado River valley, the uplands, and Baja California, O'odham peoples of Southern Arizona and northern Sonora, and the Pueblo peoples of Arizona and New Mexico.