Responding to your request:
8Reales, this is another case of me initially declining to post a reply, because I don't have the "definite" answer. There's just too darned many Civilian iron-ball possibilities. What I can tell you is that they are too big to be case-shot balls (antipersonnel balls from inside an explosive shell), except for some Heavy Caliber US Navy explosive cannonballs which used iron balls a little smaller than 1"-diameter. (See the photo below.) But that's highly unlikely to be your Maryland-dug balls, because no yankee ships shelled the Confederates anywhere in Maryland. If your finds are artillery balls, they'd have to be cannon Canister-ammo balls. (Cannon Canister ammo is a tin can filled with iron balls... firing the can caused the thin tin can to disintegrate, releasing a spray of "giant iron buckshot" balls.) Was there a Revolutionary War or War Of 1812 or civil war battle involving the use of artillery at the spot where you dug them?