Bob, the song appears to descend largely from the broadside "John and Moll," dated by the Bodleian to some time between 1790 amd 1840:

http://bodley24.bodley.ox.ac.uk/cgi-bin/acwwweng/ballads/image.pl?ref=Harding+B+25(976)&id=09760.gif&seq=1&size=0

O'Neill has a hornpipe called "Whiskey, You're the Devil," which is really the same as "Off to California," but in the key of A.