On Dec. 26, 1919 Harry Frazee, owner of the Boston Red Sox, sold Babe Ruth to the New York Yankees and consequently cursed the Red Sox for 86 years.
Check out this MLB.com article "Cursed anniversary; Babe's sale turns 90."
When Ruth was 19 years old the owner/manager of the Baltimore Orioles and the Boston Red Sox minor league team, Jack Dunn, discovered the talented pitcher and signed him.
When the other players saw the strapping young Ruth, they referred to him as "Jack's newest babe." George Herman Ruth, Jr. was known as the "Babe" ever since.
The Cincinnati Reds and Philadelphia Athletics passed on Ruth before the Boston Red Sox signed him on July 9, 1914.
On Dec. 26, 1919 Frazee sold Ruth from Boston to the Yankees after five years with the Red Sox.
Popular legend has it that Frazee sold Ruth and several others to finance a Broadway play, "No, No, Nanette."
The circumstances surrounding the trade are somewhat controversial as explained in this 2002 ESPN.com article: http://static.espn.go.com/mlb/s/2002/0718/1407265.html
Prior to Ruth leaving Boston for New York, the Red Sox had won five of the first 15 World Series. "The curse of the Bambino" had begun.
Before that point, the Red Sox had been one of the most successful professional baseball franchises. After the trade of Ruth, Boston went without a pennant for decades as the Yankees became one of the most successful franchises in professional sports.
In 2004 Boston won its first World Series in 86 years in a historic comeback against, none other than, the New York Yankees. The curse was finally broken.