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.
The United States of America is a federal democratic republic situated
primarily in central North America. It comprises 50 states and one
federal district, and has several territories. It is also referred
to, with varying formality, as the United States, the U.S., the
U.S.A., the States, or simply and most commonly, America.
The official founding date of the United States is July 4, 1776,
when the Second Continental Congress—representing thirteen
British colonies—adopted the Declaration of Independence.
However, the structure of the government was profoundly changed
in 1788, when the states replaced the Articles of Confederation
with the United States Constitution. The date on which each of the
fifty states adopted the Constitution is typically regarded as the
date that state "entered the Union" (became part of the
United States). Since the mid-20th century, following World War
II in alliance with Great Britain, the United States has emerged
as the dominant global influence in economic, political, military,
scientific, technological, and cultural affairs.
The US has the largest and most technologically powerful economy in the
world, with a per capita GDP of $40,100. In this market-oriented economy,
private individuals and business firms make most of the decisions, and
the federal and state governments buy needed goods and services predominantly
in the private marketplace. US business firms enjoy considerably greater
flexibility than their counterparts in Western Europe and Japan in decisions
to expand capital plant, to lay off surplus workers, and to develop new
products. At the same time, they face higher barriers to entry in their
rivals' home markets than the barriers to entry of foreign firms in US
markets. US firms are at or near the forefront in technological advances,
especially in computers and in medical, aerospace, and military equipment;
their advantage has narrowed since the end of World War II. The onrush
of technology largely explains the gradual development of a "two-tier
labor market" in which those at the bottom lack the education and the
professional/technical skills of those at the top and, more and more,
fail to get comparable pay raises, health insurance coverage, and other
benefits. Since 1975, practically all the gains in household income have
gone to the top 20% of households. The response to the terrorist attacks
of 11 September 2001 showed the remarkable resilience of the economy.
The war in March/April 2003 between a US-led coalition and Iraq, and the
subsequent occupation of Iraq, required major shifts in national resources
to the military. The rise in GDP in 2004 was undergirded by substantial
gains in labor productivity. The economy suffered from a sharp increase
in energy prices in the second half of 2004. Long-term problems include
inadequate investment in economic infrastructure, rapidly rising medical
and pension costs of an aging population, sizable trade and budget deficits,
and stagnation of family income in the lower economic groups.