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. Two of Tyler’s most important cabinet members were instantly lost, and the president himself had a near miss–making it the worst physical disaster to befall a presidential administration. The tragedy set off an unpredictable wave of events that cost Tyler a second term, nearly scuttled plans to add Texas to the Union and stirred up sectional rancor that drove the nation closer to civil war. Author Kerry Walters chronicles this little-known disaster that altered the course of the nation’s history.