On a bed of a primordial ocean floor and in a valley surrounded by jagged mountains, a city was founded atop the ruins of a vanished civilization. In 1867, former Confederate soldier Jack Swilling saw the remains of an ancient canal system and the potential for the area to blossom into a thriving agricultural center. Pioneers moved into the settlement searching for new opportunities, and on October 20, 1870, residents living in adobe structures that...