Green’s Dictionary of Slang

(US) a prostitute.

1909		Paducah Eve. Sun (KY) 21 Oct. 3/3: Eight workers [i.e. evangelists] [went] among the sisters in the red light district.
1913		A. Stringer Shadow 37: He could hobnob with bar-tenders and red-lighters, pass unnoticed through a slum, join casually in a stuss game .
1949		Monteleone Criminal Sl. (rev. edn) 191: red light sister A whore; a prostitute.