The purchase of Louisiana in 1803 brought French territory, which stretched from the Mississippi to parts of what is now the western United States, under American control and doubled the land area of the country. 

The United States had a "reputation as a progressive country" during two world wars and the Great Depression, a period of economic crisis in the 1930s. The United States fought the First World War alongside the Ottoman Empire, Turkey, France, Russia, Italy, Romania, Japan, Germany, Austria-Hungary, Bulgaria, and Great Britain in First World War. The US suffered from the so-called Great Recession. In 1940, President Franklin Delano Roosevelt led the country out of recession and led the United States into World War II as an ally of France and Britain against the Soviet Union, Russia, and Germany, as well as Italy and Japan. 

Colonists living in New England and areas of the New World fought and gained independence by forming a state union based on a new constitution. The Declaration of Independence, a document stating that the American colonies had fed up with being governed by Britain, now called the United Kingdom, and that the new nation was home to millions of enslaved people, states that all men are created equal. Some Native Americans spent their time navigating the vast expanses that would later become the United States of America, while others settled in certain areas to form large, enduring communities. 

Andrew Jackson is said to have noted that the United States began with the Alleghenies, implying that the west of the river was isolated and freedom from the great inner lowlands where people could escape the influences of the Old World. 

The USA, the largest country in the world, consists of a mixture of large urban areas, vast, densely populated plains, and beautiful natural landscapes. The United States is the third-largest nation in the world in terms of land and water, behind Russia and Canada, and equal with China. It is also the third-largest country in terms of landmass, larger than Europe. 

The United States is a country in North America bordering the Atlantic and Pacific oceans. The United States as a country on the North American continent consists of the 50 states of the USA, the Federal District, the District of Columbia and 14 territories. Of the 50 US states, 49 are on the US mainland and one state, Hawaii, is in the Pacific. 

The United States of America, commonly referred to as the United States of America or simply the United States of America, is the second biggest country in the world after Russia and Canada and the most populous after China and India. 

The enormous Cordillera, part of a global mountain system that surrounds the Pacific Basin, encompasses about a third of the United States and its internal diversity corresponding to its size. As a binding political union, each state has sovereignty over a separate and clearly defined geographical area and shares sovereignty with the federal government. 

The United States is among the ten largest countries in the world in terms of the number of mammals, reptiles, fish and vascular plant species. Despite its status as the world's military superpower, one of the most prosperous nations on the planet and one with the most diverse population, the No. The United States is the country with the largest number of wealthy individuals among its inhabitants, but not the richest in the world. 

The United States has had more hurricanes (300 since 1851) than any other country because of its extensive coastline, National Oceanic and Atmospheric Administration data show. In 2018 there were approximately 90 million immigrants (US-born and underage immigrants) in the United States ( representing 28% of the total US African-American population in 2017 and the largest ethnic minority and ethnic group (13% of the population of the United States). The United States has 4.5 to 20.7 million naturalized citizens, 2.7 to 12.3 million legal permanent residents, 6 to 2.2 million temporary legal residents, and 2.3 to 10.5 million illegal immigrants. 

The United States is a founding member of the United Nations, the World Bank, the International Monetary Fund, the Organization of American States, the NATO and other international organizations. The United States has the strongest higher education system in the world and attracts millions of international students every year - the most international students of any country - of all. The federal government derives its powers from the US Constitution, the oldest written constitution in the world, which is in permanent use. 

The right to vote in the elections for the President and Vice President of the United States, Members of Congress, State Executive and Judicial Officers and Members of the State Legislature shall be denied to any male resident of a State who is 21 years old or a citizen of a State of the United States; and participation in rebellion or other crime shall not be restricted in any way; nor shall the basis of representation be reduced in relation to the number of male citizens born or the total number of male citizens who are 21 years old in a State. 

In December 1941, the surprise attack of the Japanese Empire on Pearl Harbor, an American military base in Hawaii, plunged the United States into the Second World War, which had erupted in Europe for two years and since 1937 in Asia. The United States had long opposed the Third World movement that it regarded as sponsored by the Soviet Union and pursued direct actions for regime change against left-wing governments and support for authoritarian right-wing regimes.