David, I'm far from an authority on Black Bart only going by what I understood other television historians have said about him. fold 3 has him with the 116th Illinois and Wikipedia also mentioned this unit and the 116th Illinois Infantry was with Sherman and his infamous March to the Sea.
Charles Earl Boles was a reported 49er and did not do to well and moved back east later to return and did not do to well again and according to Wikipedia moved back to Decatur, Illinois prior to the war. He was born in England from what I can gather.
As I remember Black Bart left one of his monogramed hotel handkerchiefs in a failed robbery and the Pinkerton agents were able to identity the hotel and room number which took some time. The man registered at the room was Charles E. Boles and he never tried to deny being Black Bart.
Although the gold rush in California attracted tens of thousand of people it is interesting that an Englishman with a accent was reported as robbing people in 1860.
I did check with the 1860 United States census and failed to see a Charles E. Boles or Bolles or Bowles as living in Macon County, Illinois which Decatur, Illinois is located.