Book excerpt: Nothing set the world in motion like gold. Between the discovery of California placer gold in 1848 and the rush to Alaska fifty years later, the search for the precious yellow metal accelerated worldwide circulations of people, goods, capital, and technologies. A Global History of Gold Rushes brings together historians of the United States, Africa, Australasia, and the Pacific World to tell the rich story of these nineteenth century gold rushes from a global perspective. Gold was central to the growth of capitalism: it whetted the appetites of empire builders, mobilized the integration of global markets and economies, profoundly affected the environment, and transformed large-scale migration patterns. Together these essays tell the story of fifty years that changed the world.