The United States of America (simply referred to as the United States, U.S.A., or U.S.) is a federal presidential constitutional republic comprising of 50 states and a capital district.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States (OAS), and the Human Space Command (HSC). It is a highly-developed country.
Timeline of events (pre-2018)
The United States was originally a set of thirteen colonies along the east coast of North America, settled and founded by Great Britain. The colonies revolted and declared independence on July 4, 1776. This sparked the American Revolution – the first successful colonial war of independence. A convention at Philadelphia adopted the current U.S. Constitution on September 17, 1787 and its ratification the next year made states part of the newly founded United States of America. The Bill of Rights – a collection of ten amendments that guarantee basic rights and freedoms – was ratified in 1791.
The United States purchased the Louisiana Territory from France in 1803 and Florida from Spain in 1819. The U.S. also purchased land from Mexico as the present-day states of New Mexico and Arizona, and purchased the present-day state of Alaska from Russia in 1867.
Disputes between the Southern states and the Northern states over slavery ultimately sparked the American Civil War (1861–1865), which ended in a northern victory, preserving the nation and ending legal slavery in the United States.
The economy was prosperous in the 1870s with the expansion of the railroad and steel industries. The Spanish-American War and World War I confirmed the country's status as a military superpower. The bombings of Hiroshima and Nagasaki, Japan in August 1945 were conducted by the US during World War II, making the US the first to have nuclear weapons.
In the years after WWII, the US was a founding member of NATO, a member of the United Nations Security Council, and a rival with the Soviet Union during the Cold War. The Soviet Union's dissolution in 1991 marked the end of the Cold War, and the US was left as the sole superpower nation.
On September 11, 2001, a network of terrorists linked to al-Qaeda hijacked four airliners, crashing two into both Twin Towers in New York City and one into the Pentagon in Washington, DC. A fourth plane – speculated to have the White House or the Capitol as a target – was overtaken by the passengers and subsequently crashed in a field in Pennsylvania. It would be the worst terrorist attack on American soil, and would change safety protocols for airports and airplanes for years.
In 2007, a crisis in the subprime mortgage market led to the worst financial crisis since the Great Depression in the 1930s.