In an earlier entry (Poffenberger Farmstead--Rock Ledges, April 5) , I posted pictures of the rock ledges that provided cover for Semmes' and Grigsby's brigades as they advanced into action against Gorman's brigade in the West Woods. The ledges, which are present everywhere on the battlefield, are limestone outcroppings that are part of the geologic Antietam Formation.
Sometime this year at the International Conference on Military Geology and Geography in Vienna, Robert C. Whisonant will present a paper titled "No Place to Run, No Place to Hide" which will assess geology's effect on casualties. For a preview of his argument, look at a short note posted in the Civil War Librarian (see below), where Whisonant and Judy Ehlen, both geologists at Radford University, find a correlation between high casualties and the battlefield's geological formations.
"'Military people have known for thousands of years that you want to have the high ground," says Whisonant. "But there's a reason for the terrain, and that's geology.' At Antietam, for instance, the battle in Miller's Cornfield produced about half of the day's casualties in several battles, because it creates flat, open fields that proved deadly for the lines of riflemen that dominated 19th-century warfare. By contrast, a nearby struggle with a similar number of soldiers at Antietam saw fewer than half as many casualties, in part due to the dolomite rock that produced more rugged terrain." (quote from, Geology and the Civil War, Reeves Wideman , in Chronicle of Higher Education, November 21, 2008 and posted to Civil War Librarian, November 19, 2008.)
Left is a current map of the south section of the Poffenberger Farmstead showing the barn and the old road trace running through the property (click on it for a larger image).
The orientation of this map is such that the right side of the image is facing north. Gorman's brigade, and specifically the 15th Massachusetts, would be about 100 yards from the east end of the barn.
What this map shows that others do not are the the geological features that distinguish this site from the surrounding fields to the south and west. These are the rock outcroppings that gave cover to Semmes' and Grigsby's troops.
The second map shows the northern part of the property and the Mary Grove Locher cabin. Again, the stone outcroppings run through the farmstead. This is what the 15th Massachusetts faced on September 17.
The left map shows the Cultural Landscape Plan for the Poffenberger Farmstead showing the Mary Grove Locher Cabin (click to enlarge). This is what the National Park Service hopes the farmstead could be someday--restored to its September 1862 state--split rail fencing borders a restored road trace; to the east, the West Woods is reforested; and, the highway bypass is straightened to follow the farm road that connected the Poffenberger and Nicodemus farmsteads--and which for a short period of time divided the opposing brigades.