During 1940 the High Explosives plant at Kenvil, NJ had been increasing production to meet the needs of the US Armed Forces as well as our Allies involved in the war in Europe. The Kenvil munitions plant was one of several in northwest New Jersey, originally opened in 1871 to provide dynamite to the local Iron Mines.

The Kenvil facility was located in Roxbury Township, Morris County, and was owned by the Hercules Company, a spin-off from DuPont, who operated several other chemical & munitions plants in New Jersey.  Covering over 1,200 acres, dozens of major buildings processed various types of high explosives, employing hundreds of local residents who worked the various shifts at the plant. Accidents had occurred over the years at the plant, with 2 explosions in 1934 killing a total of 6 workers.

Here is the entry for "Kenvil" in a New Jersey Guidebook published in 1939:
KENVIL,  (720 feet alt., 1,000 pop.), formerly known as McCainville, advertises itself as the "Home of America's Oldest Continuously Operating Dynamite Plant" – the HERCULES POWDER Co. PLANT, founded 1871. Two major explosions brought the plant into the headlines in 1934. On March 8, four workers were killed in a packing-house blast that broke every pane of window glass in neighboring towns and shook a marine observation tower at Sandy Hook, 50 miles east. A sign was erected at the factory gate announcing that the accident was the first in 180 days, and that there had been no serious explosion on the grounds for 14 years. Five months later a detonation in the smokeless powder unit killed two men and injured three. The E. I. du Pont de Nemours Co. has had a large interest in Hercules.

At 1:30 PM on September 12, 1940 over 297,000 pounds of gunpowder blew up in a series of explosions and fires, leveling over 20 buildings. The explosions shook the area so forcefully that cars were bounced off the roads, most windows in homes miles away were broken and articles flew off shelves and walls.

The explosions were felt as far away as Poughkeepsie, N.Y., and were picked-up by the seismograph at Fordham University in New York, about 50 miles east of Kenvil. Not only were windows broken, but telephone wires were torn apart from their poles. Many windows in both Roxbury and Wharton high schools were shattered. Some told of High School students whose fathers worked at the Powder works, suddenly realizing what had happened, shrieking and running out of the building to the plant to check on loved ones.

Of course, the worst part was the loss of life. In all, 51 workers died as a result of the disaster, with over 200 injured and burned. The victims were brought to Dover General Hospital which was so overwhelmed that many individuals were just laid out on the front lawn of the Hospital, awaiting help. Victims were brought in laying in the back of pickup trucks and cars. Not only were most Doctors and Nurses from neighboring facilities called to assist, but Nursing Students from around the area spent weeks attending to burn patients. Even older Boy Scouts were used to find family members and relay messages.

Ultimately the facility was rebuilt with new safety measures and reopened in April 1941 to go on to produce munitions for World War Two as well as Rocket propellant and other products. By 1958, the Cold War was in full swing, and the Hercules Kenvil plant worked on materials for the Minuteman Missile. Smaller explosions continued from the late 1940's through the 60's, taking over a dozen additional lives. In 1964, two workers were killed in a fire in a building where smokeless powder was being prepared. In 1967 an explosion and fire leveled three buildings and killed two workers. More recently, a 1989 blast injured 20 workers and shattered glass for miles and in 1994, a machine mixing 500 pounds of nitroglycerin went up -- sending four workers to the hospital and showering the company parking lot with scraps of hot metal.

Operations at the facility ceased in 1996, the land is now fenced off and gated. Plans are being made for future uses for the large plot, with some sites needing remediation for contaminants left behind.

On September 5, 2005, a Memorial Service was held to honor the memory of the 51 people who perished 65 years earlier, and to dedicate a plaque with their names, and the names of others who died at Hercules Kenvil Works from 1917 onward. The plaque shown below is near the Memorial Garden at Horseshoe Lake Park, Succasunna, NJ.

Still unanswered is the real cause of the fatal 1940 explosion: Industrial Accident or Nazi Spies?

"PM" was a daily newspaper published in New York City from 1940 - 1948. It had a staunchly anti-fascist position and urged US intervention against Nazi Germany almost 2 years before America entered WW II. The German "Bund" was active in north Jersey, and claimed to be simply a cultural organization for those of German background. Several investigations had shown however that the Bund had many who sympathized with the Nazi regime and that their campground in Sussex county, Nordland, often hosted events and parades where young men from German background paraded in military style uniforms in the years just before World War 2. PM magazine seized upon the Hercules disaster to push US action against Germany, however most investigators concluded the plant explosion was an industrial accident, while a few kept open the possibility of sabotage.

A Box used to ship Hercules Gunpowder. 

Photo of temporary workers quarters, probably circa 1918 when WWI production was at it's peak. Notice baseball game on the field and horse-drawn carriage. This is most likely Hercules Road, just north of Rt. 46, looking northwest.

At left is a full page ad from 1918 publicizing 
the role of Hercules in the effort of WWI.