The United States became the world's first modern democracy after its break with Great Britain (1776) and the adoption of a constitution (1789). During the 19th century, many new states were added to the original 13 as the nation expanded across the North American continent and acquired a number of overseas possessions. The two most traumatic experiences in the nation's history were the Civil War (1861-65) and the Great Depression of the 1930s. Buoyed by victories in World Wars I and II and the end of the Cold War in 1991, the US remains the world's most powerful nation-state. The economy is marked by steady growth, low unemployment and inflation, and rapid advances in technology.