I checked California newspapers up to 1870 (cdnc.ucr.edu) and find lots of  
hits on "confidence man" but none for any abbreviation thereof: con man, 
con  job, &c.  Bob Stewart, Carson City
 
 
In a message dated 9/26/2013 1:43:55 P.M. Pacific Daylight Time,  
[log in to unmask] writes:

Are you  familiar with the pseudonym for a writer in the 1860s for the
St.Louis  Republican, Hans Patrick Le Connor?  I wonder if the "Le Connor"
could  be in the spirit of "Josh" and "Snook."  Were there references  to
con-men in those days?

Am grateful for your contributions  here.  Thanks

Arianne  Laidlaw
Sacramento