Green’s Dictionary of Slang

a freelance bootlegger; thus wildcatting, bootlegging.

1892		Columbus Dispatch 11 Mar. n.p.: One of the moonshiners [...] was shot in the affray. [...] Three more of the wild catters [...] are seriously hurt [DA].
1909		Salt Lake Trib. (UT) 25 July 10/1: Kentucky was formerly a stronghold of the ‘wildcatter’.
1909		Salt Lake Trib. (UT) 25 July 10/1: The term ‘moonshining’ belongs to Kentucky and Tennessee, while in Alabama the business is called ‘wildcatting’.
1910		M.Y. Tribune 11 Sept. 27/2: In Georgia they are called ‘moonshiners’; in Alabama they are known as ‘wildcatters’; in the Carolinas they are ‘blockaders’.
1913		Day Book (Chicago) 25 Jan. 3/1: He entered the united States revenue service, and trailed moonshiners, ‘wild cats’, counterfeiters and other ‘bad men’.
1938		D. Runyon ‘The Brakeman’s Daughter’ in Runyon on Broadway (1954) 505: Big False Face’s proposition [...] to sue the government for libel for speaking of brewers who supply the nation with beer after prohibition sets in as racket guys and wildcatters.
1940		S. Longstreet Decade 252: Chris [...] talked with wild-catters and night haulers.
1952		Lait & Mortimer USA Confidential 230: Ray Ryan, Hollywood oil wild-catter, used to be a 5th Street bookie. He won a well in a crap game.
1960		J.P. Donleavy Fairy Tales of N.Y. I i: I was a wildcatter in Texas and then became manager of an oil field.
1999		Observer Mag. 13 June 34: There’s still the guy from Oklahoma, the wildcatter’s son.