Battery A, the Keystone Battery, was originally organized and drilled in 1861 as a volunteer infantry company, and eventually served in the Civil War from 1862-1864 as an independent artillery battery from Pennysylvania. In 1867 the Battery was reorganized as Battery A, 1st Regiment Artillery, 1st Brigade, 1st Division, Pennsylvania State Milita, a part of the N.G.P., or Pennsylvania National Guard.

The Battery, newly armed with Gatling guns, served during labor riots in Pittsburgh in 1877, and were sent to Puerto Rico during the Spanish American War of 1898, arriving there too late, however, to see action.