The Allegheny Arsenal explosion was a catastrophic event that took place at a military munitions factory in Lawrenceville, Pennsylvania, during the American Civil War. The accident occurred on a September morning when a series of explosions resulted from the handling of artillery shells and powder. The operation of the arsenal was critical, as it supplied the Union Army with artillery and ammunition, underscoring the vast scale of war efforts at the time. Approximately 150 workers, including women and young boys, were present at the facility when the initial explosion occurred, leading to fires that rapidly spread through the arsenal's facilities.

Witnesses reported that the first explosion was followed by a series of secondary blasts, which were so powerful that they shattered nearby windows and resonated across the city. The aftermath revealed a scene of devastation as debris was scattered across a wide area and an urgent rescue operation commenced. Reports indicated that many of the victims were mothers, daughters, and young boys who played a significant role in supporting the war effort from home.

In total, around 78 people lost their lives, making it the single largest civilian loss of life during the Civil War. The tragedy prompted increased scrutiny over safety conditions in munitions factories and led to reforms in safety protocols to avoid similar incidents in the future. This disaster highlighted the human costs of warfare beyond the battlefield, reminding citizens of the dangers that lurked even while workers toiled towards a common cause.