This park in Pittsburgh’s Lawrenceville is home to an overshadowed event US Civil War history. The three large explosions at the Allegheny Arsenal on September 17, 1862 was the largest civilian disaster of the war, killing 78 workers.

The Allegheny Arsenal was built in Lawrenceville, not yet part of Pittsburgh, in 1814. A large staff manufactured ammunition to supply troops during the Mexican War and then the Civil War, numbering over 1100 at its peak.

The main building was the Laboratory near the center of the compound. Over 150 people, mostly women and girls, were making cartridges for Union troops, when at 2 PM on September 17, 1862, it is believed that a horseshoe caused a spark that would ignite stray gunpowder, which then cause one massive explosion and two others in the large building. In the aftermath, it was found that 78 staff were killed, with 54 of them being unidentifiable. They were buried in a mass grave at the nearby Allegheny Cemetery, where a memorial stands to this day. The news of the explosion was nearly lost in the aftermath of the Battle of Antietam, fought on the same day.

The buildings would be rebuilt and mainly used for storage until the land was sold off in the 20th century and then made a public park with tennis courts, basketball courts, and baseball fields. But amidst the modern revelry, Arsenal Park still contains most of the original outer wall and pre-Civil War powder magazine, now used for maintenance, with a plaque detailing the history and tragedy of the Allegheny Arsenal.