The United States declared war on Great Britain in June 1812 as the Napoleonic Wars raged in Europe. Galled by British arrogance and insults to their country, Americans had had enough. Britain, however, fielded a veteran army and powerful navy of some 700 ships-of-the-line, frigates, sloops, and minor war vessels. The U.S. Navy had only 18 frigates and smaller ships plus 165 tiny coastal and harbor-defense gunboats to potentially fight the enemy.
One of the U.S. Navy's major ships was the frigate Constellation, rated at 36 guns—one of six frigates authorized by Congress in 1794 for national maritime defense. With a crew of 340 the ship displaced some 1,265 tons and was 164 feet long on the gundeck. Under full sail with a strong wind she was capable of 15 knots. Her construction began in 1795 near Fells Point in Baltimore. Launched in 1797, she entered service in 1798.