Adam Arenson is an assistant professor of history at the University of Texas at El Paso and the author of The Great Heart of the Republic: St. Louis and the Cultural Civil War. He blogs at adamarenson.com.

This week in 1863, the celebrated Confederate General Thomas "Stonewall" Jackson was returning from a nighttime reconnaissance ride near Chancellorsville, Virginia, when he was mistakenly shot by his own camp's picket guards. On May 2, Jackson's wounded arm was amputated; Jackson's chaplain, Beverley Tucker Lacy, buried it the next day in a nearby family graveyard. Seemingly on the mend, Stonewall Jackson was removed far behind the battle lines to recuperate at Fairfield Plantation, but his condition soon worsened. Stonewall Jackson died eight days later, on May 10, 1863, of pneumonia.

General Robert E. Lee assessed the gravity of the situation for himself and the army when he first heard of Jackson's amputation. "William," Lee declared to his cook, "I have lost my right arm. I'm bleeding at the heart."

The spot where Jackson was shot is marked today by a large boulder, just behind the Chancellorsville battlefield visitor center, and the outbuilding at Fairfield plantation where Jackson died is known to this day as the Stonewall Jackson Shrine. His lost limb is buried in a graveyard off the main Chancellorsville battlefield, at what was then Ellwood Plantation. Among the unmarked graves of men and women, mothers and sons, there is one monument--to an arm....