On September 17th 1862 the Allegheny Arsenal, an important manufacturing and supply depot for the Union Army blew up.
At about 2pm on Wednesday September 17th 1862 the Allegheny Arsenal in Lawrenceville, Pennsylvania, which is located about 5 miles from Pittsburgh, Pennsylvania exploded. Colonel John Symington the commander of the arsenal rushed from his quarters when he heard the sound of the explosion. As he approached the arsenal there were two more explosions. A volunteer fire company from Pittsburgh came to assisted in fighting the fire, using a bucket brigade of water to put out the flames.
By the times the flames were out, the Arsenal had been reduced to rubble. There were 78 deaths at the lab, all workers who were mostly women. Fifty-four of the bodies were never identified and were buried in a mass grave at the Allegheny Cemetery. The explosion is thought to have been caused when a metal horse shoe made a spark in the roadway near the arsenal and set off several barrels of gunpowder. A Coroner’s Jury held Colonel Symington responsible for the explosion, as he and his subordinate had allowed loose black powder to accumulate in the roadway and around the arsenal. The military inquiry into the explosion found Symington innocent of any wrong doing.
The explosion of the Allegheny Arsenal was superseded by the news of the Battle of Antietam which took place the same day in Sharpsburg Maryland.