Green’s Dictionary of Slang

(US black) sophisticated, successful, influential.

1949		F. Brown Dead Ringer 105: ‘Rita’s no pushover for small-town bankers.’ I grinned at her; she was serious. ‘Just big-town bankers?’ I asked.
1953		L. Durst Jives of Dr. Hepcat (1989) 6: Me, ‘bigtown,’ I was king, not yet hip without scratch I wasn’t anything.