Other contributors have said "What are facts on cannon balls?" is the same question as "When was the first cannon ball made?" If you believe that these are not asking the same thing and should be answered differently, click here
The majority of the cannon balls would have been made of cast iron. Some might have been some made with steel. Hollow ones where filled with gunpowder and had a fuze that would make it explode at...
That information is lost in legends and time. ;-) For some history about the tennis ball -- including its old scottish origins from a wool-wraped stomach of a sheep or goat -- please follow this...