Green’s Dictionary of Slang

(US) that area of the town where the poor live.

1908		‘Doss Chiderdoss’ ‘The Censor’ Sporting Times 29 Aug. 1/3: He struck Bunkumville, or some such place, somewhere in U.S.A.
1908		‘O. Henry’ ‘Conscience in Art’ in Gentle Grafter (2006) 47: I saw a memorandum of expenses for a ten days’ trip to Bunkum Town made by a Pittsburg man.