The footage is of the 1925 Thanksgiving Day game between the Bears and the old Chicago Cardinals at Wrigley Field, which was then known as Cubs Field.
The three-and-a-half minute silent clip includes the first appearance in a professional game by early football star Red Grange and is the only known video of George Halas as a player.
"The first time I saw it, I couldn't believe what I was seeing," said Bears Vice President Brian McCaskey. "I felt like, wow, this is the Holy Grail of historical footage in terms of what it means to the Bears. We are so thankful to the McKearnan family for sharing it with us."