Bitch Magazine’s “Lady Liquor” series explains why, until the 1960s, American bars banned women.
Bars did employ women during the postwar era—just not to pour drinks. Instead, “B-girls” employed by the bar would show up, pretending to be nurses or secretaries on their way home from work, and charm the male clientele into buying them drink after drink. After several drinks, the woman in question—usually called a “B-girl”—would disappear, leaving her companion with an artificially inflated bar tab.
Morally reprehensible? Yes. Hilarious at a historical distance? Also yes.