Green’s Dictionary of Slang

(US) a bar that employs women whose primary job is not to dance but to promote liquor sales to the clientele.

1953		This Week 26 July 7: THIS WEEK MAGAZINE assigned girl reporter Edan Wright to get an inside story on how ‘B (for Bar) joints’ really work.
1967		(con. 1940s) M. Dibner Admiral (1968) 245: He swears she’s working this B-joint. The Oriole.
1978		T. O’Brien Going After Cacciato (1980) 131: I remember he takes me to this – you know, to this B joint.