The Trostle Barn may be the most famous structure on the Gettysburg Battlefield. Located right in the middle of the battlefield, it was the scene of severe fighting on the second day. It's nearness to The "Bloody" Wheatfield, Little Round Top, Valley of Death and The Peach Orchard place it in position of heavy fighting.

On July 2, 1863, Major General Daniel Sickles (who was later was seriously injured, near the Trostle barn, by a Confederate shell, which caused his leg to be amputated) impetiously moved his troops to an exposed position on Emmitsburg Road. Due to mounting pressure by the General Joseph B. Kershaw's Brigade of South Carolinans, the Union troops began retreating from the area of Peach Orchard.

Their goal was to make it to Cemetery Ridge. Most of the batteries were able to reach the ridge. One the "green" 9th Massachusetts Light Artillery Battery remained. Their Captain John Bigelow sustained severe wounds as the 9th Mass. Battery continued to fight, in the end, the remaining survivors fled, leaving behind their guns, limbers and also the wounded and dead, both man and animal alike.