The United States of America (USA), commonly referred to as the United States (US), America, or simply the States, is a federal republic consisting of 50 states, 16 territories, a federal district, and various overseas extraterritorial jurisdictions. The 48 contiguous states and the federal district of Washington, D.C., are in central North America between Canada and Mexico. The state of Alaska is the northwestern part of North America and the state of Hawaii is an archipelago in the mid-Pacific. The country also has five populated and nine unpopulated territories in the Pacific and the Caribbean. At 3.79 million square miles (9.83 million km2) in total and with around 316 million people, the United States is the fourth-largest country by total area and third largest by population. It is one of the world's most ethnically diverse and multicultural nations, the product of large-scale immigration from many countries. The geography and climate of the United States is also extremely diverse, and it is home to a wide variety of wildlife.
Paleo-indians migrated from Asia to what is now the US mainland around 15,000 years ago, with European colonization beginning in the 16th century. The United States emerged from 13 British colonies located along the Atlantic seaboard. Disputes between Great Britain and these colonies led to the American Revolution. On July 4, 1776, delegates from the 13 colonies unanimously issued the Declaration of Independence. The ensuing war ended in 1783 with the recognition of independence of the United States from the Kingdom of Great Britain, and was the first successful war of independence against a European colonial empire. The current Constitution was adopted on September 17, 1787. The first 10 amendments, collectively named the Bill of Rights, were ratified in 1791 and guarantee many fundamental civil rights and freedoms.
The President of the United States of America (POTUS) is the head of state and head of government of the United States. The president leads the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.
Article II of the U.S. Constitution vests the executive power of the United States in the president and charges him with the execution of federal law, alongside the responsibility of appointing federal executive, diplomatic, regulatory, and judicial officers, and concluding treaties with foreign powers, with the advice and consent of the Senate. The president is further empowered to grant federal pardons and reprieves, and to convene and adjourn either or both houses of Congress under extraordinary circumstances. Since the founding of the United States, the power of the president and the federal government have grown substantially and each modern president, despite possessing no formal legislative powers beyond signing or vetoing congressionally passed bills, is largely responsible for dictating the legislative agenda of his party and the foreign and domestic policy of the United States. The president is frequently described as the most powerful person in the world.
This is the list of all of the living people who have served as President of the United States at each moment in U.S. history. Due to the line of succession outlined in Article 2, Section 1, Clause 6 of the United States Constitution (1789), Amendment 20, Section 3 (1933) and Amendment 25, Section 1 (1967) to the Constitution, there has never been a point where there is no acting President, meaning that from the point of death, resignation or terms end of one United States President, the powers and duties of the presidency are immediately passed to his successor under U.S. law.
1909 to 1913: Theodore Roosevelt, William Howard Taft