Cobra71 wrote:
> I was just wondering if somebody could give me any information on this cannonball. [...] It
> has the seam around it with 2 plugs and measures about 5 inches across.
First... welcome to TreasureNet!

To learn my credentials for answering your info-request, go to my Profile and click on "About me." Sorry to have to say, it is definitely not a cannonball. There were no 5"-diameter cannonballs with two "plugs." Also, Mill-Balls have no need for "plugs." It is most probably either a machinery counterweight ball or a Sports Shot Put ball ...but to be more specific than that, I'll need to know the ball's super-precise diameter AND weight measurements.
SolidShotEssentialsMod
If you don't want to go to that much effort, take it to a grocery-store and weigh it on a Vegetables scale in the Produce department.
I should mention, that ball doesn't look rust-concreted enough (without cleaning) to have been in the ground for well-over 100 years. Therefore, it is probably made of steel rather than cast-iron. There is no record of steel cannonballs ever having been used in America (just cast-iron ones).