The history of the United States Navy divides into two major periods: the "Old Navy", a small but respected force of sailing ships that was also noteable for innovation in the use of ironclads during the American Civil War, and the "New Navy", the result of a modernisation effort that began in the 1880s made it the largest in the world by the 1920s.
The United States Navy recognises 13 October 1775 as the date of its official establishment, when the Continental Congress passed a resolution creating the Continental Navy. Soon after the end of the Revolutionary War the last ship was sold and the Continental Navy was disbanded. Eleven years later, conflicts between American merchant shipping and pirates in the Mediterranean Sea led to the Naval Act of 1794, which created the US Navy.
The original six frigates were authorised as part of the Act. During the next 20 years the Navy fought the French Navy in the Quasi-War, Barbary states in the First and Second Barbary Wars, and the British in the War of 1812. After the War of 1812, the Navy was at peace until the Mexican-American war in 1846, and served to combat piracy in the Mediterranean and Caribbean seas, and the slave trade. During this period the Naval Academy was founded in 1845. In 1861, the American Civil War began and the US Navy fought the small Confederate Navy with both sailing ships and ironclad ships while forming a blockade on the confederacy. After the Civil war most of the ships were laid up in reserve and by 1878 the Navy only included 6,000 men.