Allegheny Arsenal explosion kills 78 workers in Pittsburgh

Background. Established in 1814, the Allegheny Arsenal was a key Union supply center. Civilian employment grew from 308 to over 1,100 workers. The main lab employed 158 people, mostly women making cartridges. Lawrenceville, named for Captain James Lawrence, was chosen for its river access and proximity to iron production. It was annexed by Pittsburgh in 1868.

Explosion. On September 17, 1862, around 2 pm, the arsenal exploded. Seventy-eight workers, mostly young women, were killed. The most common view is that a horse's metal shoe struck a spark, igniting loose powder near the lab. Symington speculated leaking barrels caused it, a point of agreement among witnesses. The event was overshadowed by the Battle of Antietam.

Legacy. A monument near graves in Allegheny Cemetery honors the victims. Dedicated in 1928, it replaced an earlier illegible shaft. The site became Arsenal Park in 1907. Surviving buildings and stone walls became contributing properties to the Lawrenceville Historic District in 2019, which was added to the National Register of Historic Places.