"Baseball’s cheating history includes its most famous home run, the ‘Shot Heard ’Round the World’"

If you think the Houston Astros pulled off a feat with their sign-stealing en route to the 2017 World Series title, they’ve got nothing on the 1951 New York Giants. A highly similar scheme by the Giants not only sparked an amazing run to the National League pennant but also led to the most famous home run in baseball history: the “Shot Heard ’Round the World.”

Both teams used a “spy” in center field to steal the opposing catcher’s signals and relay them to the batter.

For the Astros, it was a center field camera feeding a monitor in the dugout.

For the 1951 Giants, it was a handheld telescope manned by a coach, who then pressed a buzzer that sounded in the bullpen. Both teams then signaled the pitch to the hitter — the Astros by banging a trash can, the Giants by having a player in the bullpen either toss a ball in the air or hold it still.

The Astros dominated their competition during the regular season, then won a pair of seven-game series against the Yankees and Dodgers to take the 2017 crown, winning eight of nine postseason games in their home park.

But the Giants were 7½ games out of first place on July 19, 1951, only six games above .500, when manager Leo Durocher called a team meeting to announce the new sign-stealing scheme. ...

Desperate for an edge, Durocher assigned third base coach Herman Franks to take Schenz’s portable telescope to Durocher’s clubhouse office, then located above center field at the Polo Grounds, the Giants’ home field. Durocher then had the Polo Grounds’ electrician, Abraham Chadwick, place an electric button in the office and run wires from the button to buzzers in the Giants’ bullpen and dugout, Prager discovered.

The telescope was powerful enough that Franks could easily see the opposing catcher’s signs — one finger for a fastball, two for a curveball or change-up. (Sliders and split-finger fastballs had not yet been invented.) Protective wire mesh was cut away from the glass window to remove an obstacle for the telescope, photos of the Polo Grounds show. ...

https://www.washingtonpost.com/history/2020/02/13/giants-cheating-home-run-1951/