South Dakota, cannonball, huh... any ideas?
Lots of posibilities, including a ball "liberated" from in town, by a previous resident of the ranch.
Another idea I had: The State Veterans Home, since the turn of the [last] century; & a VA Domiciliary & hospital, pre 1930s, are less than 3 miles as the crow flies, down-canyon. Both have/had old smooth bores on their grounds, and in the old days, July Fourth celebrations could get pretty wild....
In the 1870s it was quite legal to own a cannon or two for "home defense".
Custer moved through near here in the 1874 expedition; maybe?
Shucks, even in 1950s Jacksonville, OR, somebodies rolled the library/museum cannon into the street, and touched it off of an early Sunday A.M. "The Wake Up Call Heard Round The County"! Not long after, the disgruntled, humorless authorities permanently spiked it.