Green’s Dictionary of Slang

eleven forty-fiver n.

[the trad. time – 11.45 a.m. – of the pre-show parade that passed through a town where the minstrels were performing]

(US) a blackface minstrel.

[US]Miller & McBee Jr [unpub. publicity handout] in Tosches (2001) 331: ‘We are just a couple of eleven forty fivers.’ [...] ‘What is an eleven forty-fiver?’ ‘He means minstrel man. You see the minstrel shows always held a parade every day at exactly eleven forty five. That was to catch the Noon crowd.’.