When I look at photos or videos of old Major League baseball games, there is often a sign prominently displayed on a fence or scoreboard stating NO BETTING. Was this aimed at the fans, the players, or both? What penalties were there?
Here is a photo of Jim Scott, in Chicago’s Comiskey Park - sometime between 1910 and 1917. The “Black Sox” scandal took place in 1919, so the players had been warned. https://www.pinterest.ca/pin/623818985864952291/
As the Black Sox scandal (and, years later, Pete Rose) demonstrated, the penalty for a player (or member of the coaching staff) who has been found to be involved in gambling is being declared indefinitely ineligible to participate in professional baseball. In the case of the Sox players, this effectively became “banned for life” (as it has, so far, for Rose), and it has also led to such players not being named to the Hall of Fame.
A week or two ago, I caught the episode of Ken Burns’ “Baseball” documentary which dealt with the Black Sox. There, it was made clear that baseball’s leadership saw gambling as an existential crisis, and they hired Kenesaw Mountain Landis as commissioner, and gave him a lot of power, specifically to crack down hard on gambling; that concern about gambling stayed with baseball for a long, long time.
Ironically, the rules forbidding players and staff from gambling, made baseball a lot more attractive to recreational gamblers at large. With such strict penalties, competitions were less likely to be rigged the way they often were in boxing and horse racing. (at least up to the era of rampant doping).
The sign was aimed at fans. Gambling within the ballpark (with fans betting on an individual at-bat or pitch) was a common thing in the early Twentieth Century and teams made a show of being shocked by it and trying to stamp it out. Hence the oversized sign. In reality sports and gambling have always had a symbiotic relationship because gambling generates and sustains interest in sports.