A fascinating thread, that led me to sign up so I could add a related anecdote of interest.
There is a visible and possibly "live" Whitworth bolt in Gettysburg. It's lodged in the brick of the building next to the Wills' house on York Street, just under a second story window. That had to have come from Oak Hill, which measures about 1-1/4 miles away, where Hurt's Battery (Hill's corps) was firing a pair (THE pair?) of Confederate Whitworth cannon. Guides often point this artifact out, and until last year I assumed it was a 3" ball that somehow survived the weather and was protected by occasional re-pointing of the mortar around it. For years they had a small U.S. flag mounted on that windowsill, but it's been gone in recent years. From a local enthusiast I learned that what is visible is the tail end of a ten-inch Whitworth bolt.
The building was a commercial rental owned by the Wills's, and the second floor had been rented by my great-grandfather, Charles John Tyson, to house the first photo studio in Adams County. He and his brother, Isaac (who had learned photography), had left Philadelphia in 1859, and, having found studios already operating in Lancaster and York, opened their business in Gettysburg. Charles and his new bride went to Littlestown during the battle. He reported that in addition to the projectile in the wall, a minie ball had come through a rear window, which was raised. The ball made a hole without cracking the glass of the first pane, but cracked the second pane, then went through a one-inch wood partition and lodged in the far wall. Mrs. Wills prevented pillage during the three-day battle by telling Confederate troops that the studio contained "dangerous chemicals."
Tyson and 15-year-old apprentice Tipton took nearly 600 glassplate photos after the shooting stopped. But that's another story....