Great work--that's some excellent sleuthing.

I think the stage was set for executions by a decision made in October 1864 to send prisoners out of state. I imagine one reason to send them away was because of the sheer numbers of prisoners being taken; another reason might to make it easier to conduct executions. It's one thing to execute them in Macon, Missouri, in the midst of a hostile populace who would know some of the men being executed, and where word would easily spread...it's another thing to ship them off halfway to the east coast and do it there.

I'm wondering if there's a graveyard situated near to where these executions took place, which would have markers. Track down Confederate graves between March 1865 and a couple months afterwards and we might be able to pin this down even more--names, dates, etc.

Anyway, Rosecrans sent a dispatch to Halleck talking about recently captured Confederates on October 31, 1864, stating, in part, "The prisoners will be sent to prisons out of Missouri. Bill Anderson was killed on the 29th by Colonel Cox." O.R., Vol. 41, Ch. 53, Pt. 4, p. 343