USS Constitution, known as "Ol Ironsides," is a wooden-hulled, three-masted heavy frigate of the United States Navy. Named after the United States Constitution, she is the oldest commissioned ship afloat in the world. The Constitution was one of the six original frigates authorized for construction by the Naval Act of 1794 and was launched in 1797. Joshua Humphreys designed them to be the Navy's capital ships and so Constitution and her sisters were larger and more heavily armed than the standard frigates of the period.