The world's fourth largest producer of gold, America mined a bewildering 7.9 million troy ounces of the precious metal in 2017 and is estimated to have matched that amount in 2018, according to the US Geological Survey, with the state of Nevada accounting for almost 80% of the nation's output. Gold mining in the US has a long and fascinating, though often checkered, history. We take a look at the biggest discoveries in the country from the very first gold rush to the present day.