The Leadville mining district, located in the Colorado Mineral Belt, was the most productive silver-mining district in the state of Colorado and hosts one of the largest lead-zinc-silver deposits in the world. Oro City, an early Colorado gold placer mining town located about a mile east of Leadville in California Gulch, was the location to one of the richest placer gold strikes in Colorado, with estimated gold production of , worth $2.5 to $3 million at the then-price of $20.67 per troy ounce. Cumulative production through 1963 was of silver, of gold, of lead, of zinc, and of copper. The district also produced byproduct bismuth, and iron-manganese ore. History Gold was discovered in the area in late 1859, during the Pike's Peak Gold Rush. However the initial discovery, where California Gulch empties into the Arkansas River, was not rich enough to cause excitement. On April 26, 1860, Abe Lee made a rich discovery of placer gold in California Gulch, about a mile east of Leadville, and Oro City was founded at the new diggings. By July 1860 the gold rush was on; the town and surrounding area grew to a population of 10,000 and an estimated $2 million in gold (equivalent to $ million today) was taken out of California Gulch and nearby Iowa Gulch by the end of the first summer. But within a few years the richest part of the placers had been exhausted and the population of Oro City dwindled to only several hundred. Many claims were consolidated, and worked by ground sluicing. A ditch was dug in 1877 to provide water for hydraulic mining, but the hydraulic mining was reported to be unsuccessful. In 1874, gold miners at Oro City had an assay done on the heavy, black sand that had been impedeing their placer gold recovery and found that it was the lead mineral cerussite, that carried a high content of silver. Prospectors traced the cerussite to its source, and by 1876 had discovered several lode silver-lead deposits, setting off the Colorado Silver Boom. Unlike the gold which was in placer deposits, the silver was in veins in bedrock and hard rock mining was needed for recovery of the ore. The city of Leadville was founded near to the new silver deposits in 1877 by mine owners Horace Austin Warner Tabor and August Meyer, By 1878 Leadville had become the county seat of Lake county.