Timothy O'Sullivan photograph of the north end of the Slaughter Pen and Plum Run Valley, 6 July 1863--the large boulder with the trough in it is encircled.
(Gettysburg National Military Park #2B-2082)
Photo Courtesy of the Author

Confedreate dead in the Slaughter Pen, 6 July 1863--This Gardner photograph shows two dead infantrymen, probably the 44th Alabama Regiment, which suffered casualties from the rifles of the 4th Maine and from Smith's two guns on the north hillock of Houck's Ridge.
(Tipton photograph, Gettysburg National Military Park #2B-2068)
Photo Courtesy of the Author