John Rabb is in the 1850 Warren County, MS Census and listed as a planter. Apparently he died in Helena, Ark. Definitely try to locate his will and estate records.

Lots of info on John Rabb & Harriet Folkes Rabb here:
http://worldconnect.rootsweb.com/cgi-bin/igm.cgi?op=GET&db=cliffs&id=I079

"In Maple Hill Cemetery in Helena AR there is a monument to Colonel John Rabb Jr. Bart Rabb Lindsey of Helena, says the title is not from the military ,but honorary. He also explained that John Rabb is not buried there but in the family plot on the Rabb plantation south of Helena on the Mississippi River."

Mel