The clip shows FDR, who was paralyzed from the waist down by polio in 1921, grasping a rail with one hand while being supported on the other side by an assistant. FDR used a wheelchair because he could walk only with braces on his legs and the support of a cane.
"Here is FDR going to a stadium full of people," said Bob Clark, deputy director of FDR's Presidential Library and Museum. "Even the simple act of going to a baseball game required a great deal of logistics and preparation."
Former Major League Baseball player Jimmie DeShong shot the film at the 1937 All-Star game in Washington. On Thursday, the Pennsylvania State Archives in Harrisburg announced it had acquired the clip from the family of DeShong, a native of the state's capital city.
DeShong's daughter Judy Savastio said she showed the clip to officials at the FDR library in Hyde Park, New York, about two years ago. She allowed the footage to be used in a montage that has been on view at the museum for about a year.
"I was very surprised that they were so excited about it," Savastio said Friday.
Filmmaker Ken Burns calls the footage "one of the very best pieces of film that so clearly shows what a brave struggle it was for FDR to move." Burns plans to incorporate it into his upcoming documentary on the Roosevelts, which is slated to air on PBS this fall.
The footage is rare in part because not many people had personal movie cameras in those days. The press generally did not film FDR struggling to move under his own power, as the Secret Service did not want to publicize the president's vulnerability, according to historians.
The lack of historical imagery gives the impression that Roosevelt actively concealed his paralysis. But experts say he tried to minimize it to make the public more comfortable and to ensure that other nations didn't view him as a weak leader.
"Thousands of people saw him walk like that quite frequently, in person. That was no secret at all," said Ray Begovich, a journalism professor at Franklin College near Indianapolis who has researched Roosevelt's public image. "Americans knew he had polio, that he was sick and that he struggled, but they just did not know the extent of his disability."
The FDR snippet is about eight seconds of DeShong's silent footage, which overall is more than five minutes long.
The rest of the film, shot with an 8 millimeter camera during batting practice at Griffith Stadium, features a slew of baseball players, including Lou Gehrig, Jimmie Foxx, Hank Greenberg and Dizzy Dean.
Associated Press writers Kathy Matheson in Philadelphia and Rick Callahan in Indianapolis contributed to this story.
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