In the 1840s, the powerful pull of Manifest Destiny brought the U.S. Army to today's southern Arizona. The first forces came as a vanguard marching westward to conquer California, but soon their comrades returned. They would establish a string of outposts, a few of which remain more than a century after their founding. These installations greatly contributed to local military, economic, social, and even political history. Their inhabitants included noted 19th-century generals George Crook and Nelson A. Miles, as well as a later officer, Omar Bradley of World War II fame. Some of these men...