In eighteen forty-eight at Sutter's Mill, California, gold was discovered along the South Fork of the American River, and after President James K. Polk confirmed the discovery in December, a mass migration of men, women, and children from Missouri began that would peak at more than two hundred fifty thousand people traveling this route to California. Known as the "49'ers," these emigrants passed through this area on the California Trail headed toward City of Rocks. As they topped the Elba-Almo Divide, they may have seen dust trails from wagon trains traveling the Salt Lake Alternate in the distant valley, then headed south and west toward the now famous City of Rocks, a welcome campsite for weary travelers who had been on the trail for nearly one hundred days and had completed eight hundred miles of a one thousand two hundred-mile journey. In August eighteen forty-nine, William Swain wrote of traveling across Almo Valley amid the best scenery he had seen among the hills, with the snow-speckled Raft River Mountains to the south, the high bluffs of the Jim Sage Mountains to the east, Castle Rocks to the west, and a noon halt in a ravine near the splendid rock scenery of City of Rocks. By eighteen sixty-nine, completion of the transcontinental railroad, along with new gold and silver strikes in Nevada and Idaho, signaled the end of the California Trail.