The Blast That Rocked NJ

On September 12, 1940, the Hercules Powder Company Kenvil Works plant explosion killed 51 people.

Twenty buildings were destroyed and 51 people were killed in the 1940 disaster in Kenvil.
Twenty buildings were destroyed and 51 people were killed in the 1940 disaster in Kenvil.
Photo courtesy of Corbis

Seventy-five years ago, on the morning of September 12, 1940, 400 employees clocked in at the Hercules Powder Company Kenvil Works for what they thought would be a routine day. It was a lucrative time to be in the munitions business: World War II had been raging in Europe for a year, and the United States Army had placed a $2 million order at the plant for smokeless gunpowder.

The plant was founded in 1871 on 1,200 acres in Succasunna-Kenvil in Roxbury Township, which rests on one of the richest iron-ore deposits in the country (Succasunna is the Lenni-Lenape word for “black rock”). Initially, the plant made dynamite, a hot commodity in a mining town. By 1940, it was manufacturing more than 100 tons of explosives and was the only Hercules operation in the country producing smokeless gunpowder and dynamite at the same time.

At about 1:30 pm, a fire mysteriously broke out in the plant’s new solvent-recovery building. A tank containing 16,000 pounds of smokeless powder ignited, triggering explosions throughout the campus. Ultimately, 296,550 pounds of powder burst into flame, leveling 20 buildings, killing 51 workers and injuring 200 others.

The explosion registered on a seismograph at Fordham University in the Bronx, and was felt 90 miles away in Poughkeepsie. Throughout the tristate area, windows shattered and buildings shook. Nearby, the force of the explosion launched people through the air. Harry F. Pascoe, a local who later published a history of the plant titled The Powder Monkey, lived two miles from the disaster site. His family was enjoying lunch at the time of the blast; his father was scheduled to work the 3 to 11 pm shift. “The screen door suddenly opened, and I looked up to see who was coming,” Pascoe writes. “All I can remember is being under the kitchen table. Our house had sustained severe damage; my mother was crying and her arm was bleeding.”

Despite orders from the State Police, 10,000 people rushed to watch the plant burn and offer help. Bodies were laid on the front lawn of the overwhelmed Dover General Hospital. There were craters as deep as 13 feet where the buildings once stood. Today, a memorial in Horseshoe Lake Park in Roxbury honors the victims of the worst explosives-plant disaster in United States history.

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  1. Theresa Ryan Detweiler

    Today I can’t remember where I put something 5 minutes ago but i remember that day very well.My brother was killed that day. He was 18 in July and died in Sept.. After my mother picked my sister and brothers and me up from school and my Dad got home he couldn’t find Bill so he put us all in the car and went to every hospital,funeral home and hall where bodies were taken and my parents would go inside to look for Bill.We lived in Hercules Park and back then bodies were laid out at home. I turned 12 yrs. old on the 14th.I remember it well. We thanked God Dad made it out OK.