Eldorado Canyon, which runs east from here to the Colorado River, was the site of a mining boom beginning about 1859, when prospectors started digging for gold and silver and formed the Colorado Mining District. Its three largest mines—the Techatticup, Wall Street, and El Dorado Rand Group—yielded over $6,000,000. Before Hoover Dam was built, this stretch of the Colorado River was navigable, enabling steamboats and barges to freight goods 350 miles from the California Gulf to the mouth of Eldorado Canyon and upriver. Steamboat traffic peaked in the 1860s and continued until the turn of the twentieth century. In 1867, the U.S. Army established an outpost at Eldorado Canyon to secure riverboat freight and protect miners in the canyon from Native Americans, but the military abandoned the camp in 1869. The mines flourished again in the 1870s and produced ore until World War II.