American colonies gained independence from Britain in 1776, earning official recognition as the United States of America seven years later. The 19th and 20th centuries was a period of expansion in which the United States acquired overseas territories, adding 37 new states to the original 13. This period, however, was also marked by crisis.
First, the Civil War divided the nation between a northern Union of states and the eventually defeated secessionist Confederacy of 11 southern slave states. Later, the Great Depression of the 1930s brought the greatest wave of unemployment in the country’s history. U.S. successful participation in the two World Wars and the Cold War would restore national economic and political stability, elevating the country to the status of most powerful nation state.