Several of the larger guns have information printed on their muzzles, such as this 15-inch Rodman: 'Twas cast in 1861 (though reportedly none of the guns there today were mounted until after the Civil War), but more excitingly, many are marked FORT PITT PA. You know I scampered straight to Google Maps when I got home to find Fort Pitt of which, sadly, very little remains today...but it was an important foundry for the Union during the Civil War, churning out cannons-a-plenty for the cause.