In the Great Strike of 1877, a labor dispute between workers and the Pennsylvania Railroad Company set off a popular uprising. Militiamen were called in to put down the strike and clashed with disgruntled citizens. On the second day of the conflict, the Philadelphia militia retreated eastward, pursued by angry Pittsburgh residents.

Fleeing the city, the troops sought refuge at the Allegheny US Arsenal, which once stood at this location. Looking for safe-haven and reinforcements, the troops were instead turned away by the Arsenal’s commanding officer, who refused to shelter them from the furious crowd.

Left unaided, the troops retreated across the river to evade Pittsburgh’s wrath. After the troops’ flight, rioting continued for another day before dying down here, while conflict raged on in other cities throughout the country.