(Updated June 25, 2021)
On a rainy St. Louis Sunday in 1961, the Cubs became convinced the Cardinals had someone inside the Busch Stadium scoreboard who was stealing the signs of catcher Sammy Taylor.
On May 7, 1961, the Cubs and Cardinals were scheduled to play a Sunday doubleheader at St. Louis. The starting pitchers in Game 1 were Don Cardwell for the Cubs and Ernie Broglio for the Cardinals. Caldwell, who brought a 3-0 season record into the game, had pitched a no-hitter against the Cardinals the year before.
Detective work
In the doubleheader opener, the Cubs scored twice in the first inning and the Cardinals got a run in the bottom half on Ken Boyer’s sacrifice fly.
In the second, the Cardinals battered Caldwell, scoring three runs on four hits. Carl Sawatski, batting eighth in the order, drove in a run with a single and Julian Javier knocked in two with a double. The damage could have been worse if the Cardinals hadn’t had a runner thrown out at the plate.
Cubs manager Harry Craft concluded batters knew what pitches were coming and suspected it was because the Cardinals were stealing the signs Taylor gave Caldwell.
Craft said he “became suspicious when Cardinals hitters in the lower end of the batting order were hitting pitches they ordinarily wouldn’t be able to handle,” The Sporting News reported.
According to Chicago reporter Jerome Holtzman, Craft and Cubs players “discovered someone from inside the Cardinals’ left-field scoreboard was signaling on every pitch.”
“It was very simple,” Craft said. “Someone just lifted what looked like a white tile into one of the scoreboard openings every time Caldwell was going to throw a curve. When he would throw a fastball, they would just leave the opening black.”
The switcheroo
Craft and Caldwell came up with a plan to cross up the Cardinals.
Craft told Taylor to give the sign for a curve, but to expect Caldwell to throw a fastball.
When Boyer came to the plate to lead off the third for the Cardinals, Taylor gave Caldwell the sign for a curve. Boyer leaned “way over the plate,” Craft told The Sporting News, in anticipation of a breaking ball.
Instead, Caldwell buzzed a fastball near Boyer’s chin and the pitch nearly hit him.
For the remainder of the game, the Sporting News reported, “there was no more signaling from the scoreboard.”
Caldwell held the Cardinals scoreless for the next three innings. The game was called after five innings because of rain and the Cardinals, on the strength of those early runs, won, 4-2. Boxscore
Do unto others
Two months later, on July 1, 1961, when the Cubs beat the Cardinals, 13-1, at Wrigley Field in Chicago, the Cardinals accused the Cubs of spying.
Cardinals manager Solly Hemus “charged that the Cubs have been stealing the catcher’s signs the past two days by placing a spy in center field,” the St. Louis Post-Dispatch reported.
Cardinals catcher Jimmie Schaffer said “he noticed that a red television light in center field would blink when he called for a fastball,” the Post-Dispatch noted.
Schaffer added, “If it was a curve, the light didn’t blink.”
According to the Post-Dispatch, a Cardinals pitcher was sent to the center field seats “as a counter-spy.” Boxscore
RetroSimba 
The Cubs have always been involved one way or another in sign stealing controversies. During the 1950’s, the Cubs were accused of having a light hanging from the end of the scoreboard. If a curveball was coming, it would flash. In a game they had with Braves in 1961 at Wrigley, the Cubs accused Braves pitchers Bob Buhl and Joey Jay of flashing signs from the stands in center field. Interestingly, Buhl would join the Cubs in 1963! It’s funny, with the Cubs, Don Cardwell beat the Cardinals four times. For his career though, he was 5 and 19.
Thank you. I didn’t know the history of the Cubs’ sign-stealing tricks.