Oro City, Colorado

Oro City was the site of one of the single richest placer gold strikes in Colorado, with estimated gold production of 120,000 to 150,000 troy ounces (4 to 5 metric tons), worth $2.5 to $3 million at the then-price of $20.67 per troy ounce (31.1 grams).

It is in California Gulch, about a mile (1.6 km) northeast of Leadville in the Mosquito Range of Lake County, Colorado, United States.

However the initial discovery, where California Gulch empties into the Arkansas River, was not rich enough to cause excitement.

On 26 April 1860, Abe Lee made a rich discovery of placer gold on California Gulch six miles (9.7 km) east of the Arkansas River, and Oro City was founded at the new diggings.

Some veins of gold ore had already been found, but following the brown sand to its sources in the bedrock led to the discovery of large and rich silver deposits.