A fire onboard the cargo ship SS Grandcamp docked at Texas City in 1947 detonated 2,300 tons of ammonium nitrate, a compound used in fertilizers and high explosives. The explosion blew two planes out of the sky and triggered a chain reaction that detonated nearby refineries as well as a neighboring cargo ship carrying another 1,000 tons of ammonium nitrate. The disaster killed roughly 600 people and injured roughly 3,500, and is generally considered the worst industrial accident in U.S. history.
In 1917, a French cargo ship fully loaded with explosives for World War I accidentally collided with a Belgian vessel in the harbor of Halifax, Canada. It exploded with more force than any man-made explosion before it, equivalent to roughly 3 kilotons of TNT. The blast sent a white plume billowing 20,000 feet (6,100 meters) above the city and provoked a tsunami that washed up as high as 60 feet (18 meters). For nearly 1.2 miles (2 km) surrounding the blast center, there was total devastation, and roughly 2,000 people were killed and 9,000 injured. It remains the world's largest artificial accidental explosion.