On the morning of January 24, 1848, James W. Marshall discovered gold in California. The news spread across the continent, launching hundreds of ships and hitching a thousand prairie schooners filled with adventurers in search of heretofore unimagined wealth. Those who joined the procession—soon called 49ers—included the wealthy and the poor from every state and territory, including slaves brought by their owners. In numbers, they represented the greatest mass migration in the history of the Republic. In this first comprehensive history of the Gold Rush, Malcolm J. Rohrbough demonstrates that in its far-reaching repercussions, it was the most significant event in the first half of the nineteenth century. No other series of events between the Louisiana Purchase and the Civil War produced such a vast movement of people; called into question basic values of marriage, family, work, wealth, and leisure; led to so many varied consequences; and left such vivid memories among its participants. Through extensive research in diaries, letters, and other archival sources, Rohrbough uncovers the personal dilemmas and confusion that the Gold Rush brought. His engaging narrative depicts the complexity of human motivation behind the event and reveals the effects of the Gold Rush as it spread outward in ever-widening circles to touch the lives of families and communities everywhere in the United States. For those who joined the 49ers, the decision to go raised questions about marital obligations and family responsibilities. For those men—and women, whose experiences of being left behind have been largely ignored until now—who remained on the farm or in the shop, the absences of tens of thousands of men over a period of years had a profound impact, reshaping a thousand communities across the breadth of the American nation.