On the evening of May 2, 1878, the Washburn A Mill exploded in a fireball, hurling debris hundreds of feet into the air. In a matter of seconds, a series of thunderous explosions—heard ten miles away in St. Paul—destroyed what had been Minneapolis' largest industrial building, and the largest mill in the world, along with several adjacent flour mills. It was the worst disaster of its type in the city's history, prompting major safety upgrades in future mill developments.