Gamblers were often visibly present at ballparks and the fixing of games had been suspected since the mid-1850s. Rumors circulated that players supplemented their incomes by throwing single games. Several ballplayers had the reputation of working closely with gamblers. A small-time gambler, Joseph Sullivan, allegedly made money on inside tips from Chicago's Chick Gandil. Sullivan's bets were safer when he knew a pitcher or hitter was sick, hurt, or having an off week.

Although gambling was intertwined with baseball long before the eight White Sox were accused of fixing the Series, the number of gamblers at ballparks had dramatically increased by 1919. Ironically, Comiskey posted signs throughout the park declaring, "No Betting Allowed In This Park." Unfortunately for Comiskey, the signs were not enough. Player resentment was high and gamblers' offers, which were sometimes several times a ballplayer's salary, were too tempting to refuse.