Bruce, have you looked very closely at Capt. Richard G Chitwood as a possibility for one of your "unidentified yanks"?

Name:Richard G Chitwood
Post Name: Laramie River Camps (WA) - Ligton, Convict Camp (PI)
Post Commander: Joseph J Gravely
Military Place:Cavalry Missouri State Militia
Return Period:Aug 1863

A note on the returns indicates that he was in Springfield at the right time.