The Continental Navy was established in October, 1775, to support the Continental Army during the War of Independence (1775-83). Its main activity was to attack British merchant shipping during the conflict. It was disbanded in 1784 but was re-established by Congress in 1798 to protect U.S. merchant ships from pirate attacks.

The United States Navy played an important contribution to the Union victory during the American Civil War by mounting a blockade of Confederate seaports.

On the outbreak of the First World War, the United States Navy, with its 300 warships, was the third largest in the world. These warships were used to protect merchant and troopships across the Atlantic. Some warships were also sent to the Mediterranean but most remained on the Atlantic seaboard of the USA. The US Navy's most serious wartime losses were the cruiser San Diego sunk by mines from a U-boat off New York, and two destroyers lost on anti-submarine work in European waters.

After the Japanese attack on Pearl Harbor, on 7th December, 1941, Franklin D. Roosevelt ordered a building programme that eventually made it the largest navy in the world. In 1941 the United States Navy had 300,000 officers and by the end of the war this had reached 3,000,000.

Since the Second World War the United States Navy has maintained its position as the largest and most powerful in the world. It built the world's first nuclear-powered submarine in 1954 and the first nuclear-powered aircraft carrier in 1961.