In October 1861, Colonel Baker was authorized to increase his command to a brigade. The additional regiments were commanded by Colonels Joshua T. Owen, DeWitt Clinton Baxter, and Turner G. Morehead, all from Philadelphia, respectively designated the 2nd, 3rd, and 5th California Regiments. The 4th California Regiment, as planned, was composed of artillery and cavalry. These troops were soon detached. After Baker was killed in the Battle of Ball's Bluff, Pennsylvania claimed these four infantry regiments as a part of its quota, and they became known as the "Philadelphia Brigade" of Pennsylvania Volunteers. They were initially commanded by Brig. Gen. William W. Burns and first served in John Sedgwick's Division of the II Corps, Army of the Potomac. They had a distinguished service career, highlighted by their actions at the Battle of Antietam and their prominent position in the defense against Pickett's Charge at the Battle of Gettysburg.