ON THIS DAY: May 18, 1918, Oakdale factory explosion kills 200

OAKDALE, Pa. — The stagnated trench warfare of World War I had been raging overseas for nearly two years when the United States ended its neutrality in 1917. American companies had already been awarded lucrative contracts by the Europeans, but the entry of the nation itself into the war opened the floodgates of federal spending.

The Aetna Explosives Company, based in New York City, found itself in the right place at the right time. Its subsidiary, the Aetna Chemical Company, had built a factory a mile south of Oakdale on a 15-acre parcel in 1915. Flush with European demand for munitions, the company specialized in the production of TNT (Tri-nitro-toluene), which was ideal for trench warfare.

The factory’s production created noxious pollution in Oakdale and accidents caused alarm among the residents. When five workers were killed in an explosion in September 1916, residents requested the plant be relocated away from the town. The United States’ entry into the war ended their quest.

Reliant on an immigrant workforce, Aetna Chemical built employee housing on the hill behind the factory. The company was pushing to fulfill an order from the Bureau of Ordnance for 14.5 million pounds of TNT using a new chemical called Dynol that lowered production costs.

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Aetna Chemical Company factory in Oakdale Aetna Chemical Company factory in Oakdale (Oakdale History Room)

Midday on May 18, 1918, residents of Oakdale were startled by a low rumble that drew their eyes to massive cloud billowing into the sky above the Aetna plant’s location. Rescuers rushed to the plant, trying to save anyone they could.

Word of the disaster spread quickly. Families, recovery workers and onlookers poured into Oakdale. Among them were doctors and nurses in town for a Red Cross parade the morning of the blast. Many were meant to be shipping out to Europe but instead found themselves rushing to the carnage in Oakdale, alerted by newsboys.

Around 2 p.m. a second explosion rocked what was left of the plant, killing workers and would-be rescuers alike. Explosions rolled through the remains of the plant throughout the afternoon, trapping dangerous fumes in the valley and leaving much of the site inaccessible due to the extreme heat.

The devastation was so great that the final death toll was calculated by the company’s timekeeper counting the number of employees not killed, which was complicated as the company’s records were destroyed in the blast. Only 93 victims’ remains were officially identified and at least 107 people were missing, likely incinerated completely by the explosions and subsequent fires. The county coroner ordered a census of the town in an attempt to clarify the number of dead. Many people were injured from flying debris and body parts were found over a mile away from the blast.

Allegheny County officials estimated that the town’s normal population of 2,000 swelled to 50,000 within days. The Allegheny County sheriff had to deputize nearly 100 men just to help control the scene as train after train arrived from nearby Carnegie.

The Bureau of Explosives, in conjunction with an Aetna Chemical investigation, determined that an earlier federal order to change the process of drying Dynol had not been followed. The resulting mixture was too volatile, setting off the initial explosion.

The plant never fully reopened and Aetna shifted most production to Mount Union. With the end of the war that November, military contracts dried up.

According to the National Fire Protection Association, the catastrophe remains the deadliest fire or explosion in a manufacturing plant in U.S. history.

A monument to the tragedy stands in the cemetery above the plant site. Carved into the monument is the phrase: “Like soldiers, they died in their country’s service.”

Ruins of the plant are still visible off Noblestown Road and along Robinson Run, which roughly parallels the Panhandle Trail.

West Allegheny School District social studies teacher Daniel Prevade has written extensively on the explosion. His story, “Horror and Heroism,” is available by clicking here.

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