Wednesday marks the 146th anniversary of one of the most deadly accidents in Pittsburgh history: the explosion at the former Allegheny Arsenal in Lawrenceville.

The disaster killed 78 people, mostly women and girls, and plunged the city into a week of mourning. The accident was reported in the New York Times but otherwise received little notice outside Pittsburgh because it took place on Sept. 17, 1862, during the Battle of Antietam, the bloodiest day of the Civil War.

"When you look at thousands being killed, compared to 78, that took precedence over this," said Allan Becer, a Lawrenceville historian.

The arsenal was founded in 1826 on 30 acres along both sides of Butler Street.

"One of the reasons they established it here in Pittsburgh was because at that point in time, this was the gateway to the West," Becer said.

The facility reached its peak during the Civil War when it supplied Union troops with cartridges, saddlebags, stirrups, caissons and gun carriages. The number of employees soared from 308 before the war to more than 1,100 during the war.

Of those, 156 worked in the laboratory on the day of the explosion.

To this day, no one knows for sure what happened at 2 p.m. on Sept. 17, 1862.

The most popular view is that a metal horseshoe struck a spark that ignited loose powder. In a letter to the Ordnance Department, Col. John Symington, commander of the arsenal, blamed "the leaking out of powder when one of the barrels was being placed on the platform."

A series of three explosions reduced the lab to rubble. Women wearing hoop skirts could not escape through windows, said James Wudarczyk, a researcher for the Lawrenceville Historical Society.

"It was gruesome," he said. "They would find an arm here and a leg there."

In 1926, the government sold off the last parcels. Arsenal Park now occupies the site.

In the book, "Buildings of Pennsylvania: Pittsburgh and Western Pennsylvania," to be published next year, author Lu Donnelly writes that all that remains of the arsenal are a powder magazine, the perimeter wall, stone piers and some post-Civil War buildings.

The victims are buried in Allegheny and St. Mary cemeteries in Lawrenceville. The government provided no compensation, Becer said, just coffins for the unidentified victims.

Additional Information:

Pitt Fact

Col. John Symington, commander of Allegheny Arsenal, had a famous nephew. Who was he?

A. Author Mark Twain

B. Vice President Andrew Johnson

C. John Wilkes Booth, assassin of Lincoln

D. George Pickett

Answer: George Pickett, the Confederate general who led the charge at Gettysburg

Source: Allan Becer, Lawrenceville historian

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