Why was it there?
"The guy hit a bunch of home runs, so we put a plaque up," Hall president Jeff Idelson said, referring to Ruth's 714 home runs.
But seriously, folks.
"It's the first time it has been moved out of the museum, and it's in celebration of a few different things," Idelson said.
The plaque will travel on Wednesday to Grand Central Terminal, where it will be one of the highlights of the traveling program, "Path Through History," and be available for viewing in Vanderbilt Hall from 11:30 a.m. to 6:30 p.m. ET.
It's the 100th anniversary of Ruth breaking into the Major Leagues, and a new Ruth Gallery will open in the Hall as part of the Museum's 75th anniversary celebration in Cooperstown on June 12-13.
"It's here for the display tomorrow, but we figured why not bring it next door to the House that Ruth Built to show it off?" Idelson said.
Ruth opened the original Yankee Stadium across 161st Street on April 18, 1923, by hitting a home run in the Yankees' 4-1 victory over the Red Sox.
The Bambino was elected to the Hall of Fame in 1936 in the first class, which included Ty Cobb, Walter Johnson, Honus Wagner and Christy Mathewson. Those five are the centerpiece of the famous plaque gallery, and visitors to the Museum on Tuesday found a message in the spot usually reserved for Ruth that his plaque was traveling elsewhere.
To illustrate how rare it is for a plaque to leave the gallery, it is only the fourth time in recent years that one has traveled elsewhere. When that happens, it is placed in a black metal case and protected by a member of the Museum's security staff.
Jackie Robinson's plaque went to Los Angeles last year for the premiere of the film "42," and the plaques honoring Duke Snider and Harmon Killebrew went to ballpark memorial services when both players passed away in 2011.
"That's incredible, something to see," Yankees captain and shortstop Derek Jeter said, when told that Ruth's plaque was on the field.
Told that he would be joining Ruth five years from his impending retirement at the end of the season, Jeter laughed.
"Hey, hold on," he said. "I'm not ready to go there yet."