The official currency is USD, American Dollar.  We recommend an exchange before the trip at Forex or another currency exchanger to be able to pay for any transport from the airport, food and drinks on site and the first time on holiday. Avoid carrying around too much cash.  The US is a country built around cash trading, which is usually recommended. But the country is modern enough to take cards everywhere. However, avoid using your card in less shady shops.  Some shops only accept cash but usually have their own ATM in the shop in these cases.