What role did mining play in westward expansion?

Mining for gold and silver brought prospectors and white settlers into many areas including South Dakota, Colorado, Nevada, and California. Because gold was the standard of currency throughout the world economy, gold was essential to keep the country open to trade with European nations. During the Civil War, gold and silver mines were sources of revenue to keep the war going. Later, mining for other commodities like coal, mica, copper, and mercury caused other communities to spring up.