The Pennsylvania National Guard is one of the oldest and largest National Guards in the United States Department of Defense. It traces its roots to 1747 when Benjamin Franklin established the Associators in Philadelphia.

The Great Railroad Strike of 1877, sometimes referred to as the Great Upheaval, began on July 14 in Martinsburg, West Virginia, after the Baltimore and Ohio Railroad (B&O) cut wages for the third time in a year. The Great Railroad Strike of 1877 was the first strike that spread across multiple states in the U.S. The strike finally ended 52 days later, after it was put down by unofficial militias, the National Guard, and federal troops. Because of economic problems and pressure on wages by the railroads, workers in numerous other states, from New York, Pennsylvania and Maryland, into Illinois and Missouri, also went out on strike. An estimated 100 people were killed in the unrest across the country. In Martinsburg, Pittsburgh, Philadelphia and other cities, workers burned down and destroyed both physical facilities and the rolling stock of the railroads—engines and railroad cars. Some locals feared that workers were rising in revolution, similar to the Paris Commune of 1871, while others joined their efforts against the railroads.