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.