Paleo-indians migrated to what is now the United States mainland, from Asia, around 12,000 years ago, and developed a maize-based agriculture which supported population growth and craft specialization. After European explorers and traders first made contact, largely in the 16th century, it is estimated that the local population declined due to various reasons, including diseases such as smallpox and measles to which indigenous Americans had no natural immunities.
The United States emerged from 13 British colonies, after the first successful war of independence against a European colonial empire. The current Constitution was adopted in 1787, with 10 amendments, collectively named the Bill of Rights, being ratified in 1791.
America's gross domestic product accounts for close to a quarter of the world's total, and its military budget is reckoned to be almost as much as the rest of the world's defence spending put together. The country is also a major source of entertainment, ranging from television, Hollywood films, jazz, blues, rock and rap music.
Politics in the United States is dominated by two major party coalitions, the Democratic Party and the Republican Party. The Democratic Party evolved from the party of Thomas Jefferson in the late 1700s, while the Republican Party was formed by a coalition opposed to slavery in the 1850s.
Other Main Cities:
International Dialling Code: