United States

The United States of America is a federal republic covering approximately 9.83 million square kilometres — the third or fourth largest country in the world depending on how disputed borders are counted. It stretches from the Atlantic Ocean to the Pacific, plus the non-contiguous states of Alaska (bordering Canada in the far northwest) and Hawaii (a chain of Pacific islands roughly 3,900 km from the US mainland). As of the mid-2025 Census Bureau estimate, the US population is approximately 342 million people, making it the third most populous country after India and China. Population density is relatively low at around 37 people per square kilometre, but distribution is dramatically uneven — the northeastern corridor from Boston to Washington DC is one of the world's densest urban regions, while much of the interior West is nearly empty.

The country is a federal presidential constitutional republic. Political authority is divided between the federal (national) government and 50 state governments, with substantial powers held at both levels. The federal government has three coequal branches: executive (the President — currently Donald Trump, 47th president, serving a second non-consecutive term after being inaugurated on 20 January 2025; Vice President JD Vance), legislative (Congress: 100 senators — two per state — and 435 voting representatives allocated by state population; the 120th Congress will convene in January 2027 following the November 2026 midterms), and judicial (the Supreme Court and federal court system). Each state has its own constitution, governor, legislature, and court system, and states retain broad authority over criminal law, family law, education, land use, and most everyday regulation — which is why our sister site State Law Handbook exists as a companion reference for the state-by-state legal landscape.

The US is the world's largest economy with nominal GDP of roughly $30 trillion in 2025 — approximately 25 percent of global economic output, with the US dollar serving as the world's primary reserve currency and unit of account for global trade. The country hosts a disproportionate share of the world's top universities, largest technology companies, most-watched cultural exports (Hollywood, music, sports), and most-visited attractions. It also has one of the world's most diverse populations by ancestry: European (of many origins), African American, Latino / Hispanic (Mexican, Puerto Rican, Cuban, Central American, South American), Asian American (Chinese, Indian, Filipino, Vietnamese, Korean, Japanese, and others), Native American, Middle Eastern, and Pacific Islander communities all contribute to the American cultural fabric. English is the de facto national language (spoken at home by roughly 78 percent of residents); Spanish is spoken at home by roughly 13 percent, making the US the country with the second largest number of Spanish speakers in the world after Mexico.

One of the most-confused points about the US is the difference in status between the 50 states, the federal district (DC), and the various US territories. Everyone born in a state or DC is a US citizen at birth. Everyone born in Puerto Rico, the US Virgin Islands, Guam, or the Northern Mariana Islands is also a US citizen at birth. But American Samoans are US nationals, not citizens (unless naturalised). And representation in Congress, electoral votes in presidential elections, and federal taxation all differ. The table below untangles the main categories.

In addition to the seven categories above, the US administers a handful of uninhabited or minimally-populated islands (Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Atoll, Palmyra Atoll, Wake Island, Navassa Island). Some are National Wildlife Refuges. None have permanent civilian populations.

Air travel is the practical default for cross-country trips. The US has the world's largest and most-developed aviation network, with over 5,000 public airports. The largest hubs include Atlanta (ATL) — often the world's busiest airport by passenger traffic — Dallas-Fort Worth (DFW), Denver (DEN), Chicago O'Hare (ORD), Los Angeles (LAX), and the New York metro's three airports (JFK, LGA, EWR). Major domestic carriers are American Airlines, Delta, United (the "Big Three" legacy carriers with international routes and hub-and-spoke models), plus Southwest (low-cost, point-to-point, no assigned seats — enormously popular for domestic travel), JetBlue, Alaska Airlines, Spirit, and Frontier. A cross-country flight (New York to Los Angeles) takes about six hours.

Trains: Amtrak. The US does not have European or Japanese-style high-speed rail. Amtrak is the national passenger rail operator; its most-used and most-competitive services are on the Northeast Corridor (Boston-New York-Philadelphia-Baltimore-Washington DC), where the Acela Express provides fast intercity rail comparable to European services. Other Amtrak routes cover the West Coast, Chicago hub, and long cross-country journeys like the California Zephyr (Chicago to San Francisco), Coast Starlight (Seattle to Los Angeles), and Empire Builder (Chicago to Seattle) — spectacular scenic trips that take days but are experiences in themselves. Freight rail dominates America's rail network; passenger rail plays a much smaller role than in most peer countries.

Roads and driving. The US Interstate Highway System (over 77,000 km) is the country's most-consequential piece of infrastructure — the world's longest limited-access highway system. Renting a car is straightforward for foreign visitors with valid driver's licences (an International Driving Permit is recommended but not required for short visits); minimum rental age is usually 21 or 25. Driving is on the right. Speed limits typically 65-80 mph (105-130 km/h) on interstates. Gasoline prices vary substantially by state (California is expensive; Southern states are cheaper). Rules of the road and specific state law — including licensing reciprocity, DUI rules, right-turn-on-red variations, insurance minimums, and cannabis-and-driving rules that have changed significantly with state cannabis legalisation — vary state to state; our sister site State Law Handbook covers state-by-state driving law in detail.

Urban transit works well in a handful of US cities. New York City has the country's most-comprehensive rapid transit system — the subway is 24/7 and covers the entire city; Manhattan is walkable and most residents do not own cars. Washington DC, Boston, Chicago, Philadelphia, San Francisco, and Los Angeles (increasingly, with the LA Metro expanding) have functional subway/metro systems. Most other US cities are car-dependent, though ride-hailing (Uber and Lyft) is nearly universal. Intercity buses (Greyhound, Megabus, FlixBus, Peter Pan) serve many corridors at low cost. Amtrak Northeast Corridor and the Northeast's regional commuter rail networks (LIRR, Metro-North, NJ Transit, SEPTA, MBTA) are functional urban and regional transport.

Visa & entry. Citizens of 42 countries participate in the Visa Waiver Program (VWP) and can travel to the US for tourism or business for up to 90 days with an approved ESTA (Electronic System for Travel Authorization) instead of a visa. VWP countries include most EU states, the UK, Ireland, Australia, New Zealand, Japan, South Korea, Singapore, Taiwan, Israel, Chile, and others. ESTA is applied for online, costs $21 (as of 2025), and is valid for two years or until passport expiration (whichever is shorter). Citizens of countries not in VWP typically need a B-1 (business) or B-2 (tourism) visa obtained in advance at a US embassy or consulate. Rules can change — always confirm current requirements with the US State Department before travel. On arrival: fingerprints and a photo are taken at CBP (Customs and Border Protection); an interview with a CBP officer is standard.

Currency. The US dollar (USD, $) is issued by the Federal Reserve. It is the world's primary reserve currency and is used in roughly 88 percent of foreign exchange transactions globally. Denominations: coins ($0.01 penny, $0.05 nickel, $0.10 dime, $0.25 quarter, plus rarer $0.50 half-dollar and $1 coins) and bills ($1, $2 rare, $5, $10, $20, $50, $100). US bills are all the same size and predominantly green — the "greenback." Larger bills ($50, $100) are sometimes refused at small businesses; smaller denominations are more practical. ATMs are universal. Foreign-issued cards work at most ATMs; expect a small foreign transaction fee.

Card payment is nearly universal — contactless (tap-to-pay), chip-and-PIN, and swipe are all accepted. Apple Pay, Google Pay, and Samsung Pay work at most modern payment terminals. Some smaller cash-only establishments still exist. Many places, particularly in service industries, add a "kitchen appreciation," "wellness," "service," or credit-card-processing surcharge — check receipts. Sales tax is added at the register in most states (not printed on displayed prices) and varies enormously — from 0 percent (Oregon, Montana, New Hampshire, Delaware, Alaska has no state sales tax) to 8-10 percent in cities like New York and Chicago.

Connectivity. Excellent 4G/5G LTE coverage across urban and most rural areas. Major carriers are Verizon, AT&T, and T-Mobile. eSIM options for visitors — Airalo, Nomad, Holafly, Ubigi — are widely available and often much cheaper than international roaming. Physical SIM cards are available at airports and mobile carrier stores (bring passport for registration). Free Wi-Fi is standard in coffee shops, hotels, restaurants, most public libraries, many transit systems, and many entire downtown districts. Public Wi-Fi security is generally acceptable but a VPN is recommended for sensitive activity.