Esteemed member "Susan S. Wittenberg"
The Third Pennsylvania CAvalry was part of Col. J. Irvin Gregg's brigade of the Second Division, Cavalry Corps, ARmy of the Potomac. It was made up of Philadelphians. Its men participated in the great cavalry battle on the East CAvalry Field. One of its members, Capt. Miller, won the Medal of Honor for leading the final, crushing Union charge of the day. Its other most prominent member, Lt. William Brooke-Rawle became a cavalry historian after the battle, and is the lowest ranking officer to have a monument on the battlefield.
One of the best cavalry unit historys to come out of the AOP was "History of the Third Pennsylvania Cavalry" edited by William Brooke-Rawle. Published in 1905 by Franklin Printing Company originally then reprinted some years ago by Morningside. Unfortunately now out of print, you may be able to find a copy in the usual used book sellers. I ran onto several copies at Olde Soldier Books a couple of years back. They were going for a couple of hundred bucks then and those were the reprints! But if your unit wants a unit history that is the only way to go.