Well, there was also John "Cockeye" Dunn, although I don't know if he could be considered a boss or rather a second-in-command for Eddie McGrath. Also, Rosario Borgio, a rather prominent gangster in Akron, died on the chair, although I am not sure if he was Cosa Nostra or just a "black hand" gang; and Dominic Benigno, a boss from Cleveland in the first 20s, for a double murder/robbery, he was considered the first boss of the Mayfield Road Mob.

Several other gang bosses have been also executed, although not on the chair, but on the gallows:

Sam Cardinelli (Chicago)
Rocco Racco (Pennsylvania)
Charlie Birger (southern Illinois)

Just for the record