In 1844, the USS Princeton" was the most technologically sophisticated warship in the world. Its captain, Robert Stockton, and President John Tyler were both zealous expansionists, and they hoped that it would be the forerunner in a formidable steam-powered fleet. On a Potomac cruise intended to impress power brokers, the ship's main gun--the Peacemaker--exploded as the vessel neared Mount Vernon. Eight died horribly, while twenty others were injured...