Potosí was founded as a mining town in 1546, while Bolivia was still part of the Viceroyalty of Peru. Over the next 200 years, more than 40,000 tons of silver were shipped out of the town, making the Spanish Empire one of the richest the world had ever seen. But such vast wealth also came at a price. Thousands of the indigenous people were forced to work at the mines, where many perished through accidents, brutal treatment, or poisoning by the mercury used in the extraction process. Around 30,000 African slaves were also brought to the city, where they were forced to work and die as human mules.