Britain's American colonies broke with the
mother country in 1776 and were recognized as the new nation of
the United States of America following the Treaty of Paris in 1783.
During the 19th and 20th centuries, 37 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.