A "gold rush" is a brief period of frenzied migration to a distant region of the world where large quantities of easily accessible gold have recently been found. The "rush" is necessary to get there fast before all the "easy pickings" are gone.
The term "gold rush" is most commonly used in reference to several such incidents around the Anglophone World in the mid 19th century. Although there were earlier, smaller-scale "gold rushes" such as the Georgia Gold Rush of 1829, the first great gold rush was the California Gold Rush of 1848-50, which drew prospectors from around the World. This was followed shortly thereafter by the New South Wales Gold Rush and the Victorian Gold Rush in Australia and later by the South Otago Gold Rush (1861) and the West Coast Gold Rush (1864) in New Zealand.
South Africa saw the Witwatersrand Gold Rush of 1886, which brought the British into direct conflict with the Boers for the first time and revolutionized South Africa's economy. The Klondike Gold Rush in Canada's Yukon Territory (1896–99) closed out a century of gold rushes, and is remembered as the "last great gold rush."