How did the Yankees, Red Sox feud start?
I wouldn't call it a feud. But it is a hell of a rivalry. The history goes back to 1920. The Red Sox were an excellent team in the 1910s, especially after signing an excellent pitcher who also hit pretty good by the name of Babe Ruth. Meanwhile the Yankees were a bad team that did not even have it's own ballpark, instead leasing space from and playing second fiddle to the New York Giants. In 1920, hurting for cash, the Red Sox owner sold Babe Ruth and several other players to the Yankees, in part to generate cash to produce a Broadway play. The Yankees suddenly got very good and the Red Sox got very bad … for many years. The Red Sox failed to finish higher than 4th place from 1919 to 1938. In fact, the Yankees got so good that the Giants tossed them out of the Polo Grounds and Yankee Stadium was built.Up until the 1970s, the Yankees and Red Sox were rarely good at the same time, with the exception of some years during the Ted Williams eroa, late 30s through the 50s when the Red Sox went to a single world series, and had a few 2nd place finishes. This changed in the 70s when both teams were good with the Sox going to the World Series in 1975 and the Yankees the following three years. Both teams had some gritty hard nosed players such as the catchers on each team: Carlton Fisk and Therman Munson. There was a brutal fight between the teams in 1976. In 1978, the Yankees made up a huge deficit in the standings against the Red Sox and wound up tied, forcing a one game play off for first place which the Yankees won after being behind. The rivalry was on fire.Since then, the teams have often been first and second in the standings. They are now playing their fourth playoff series against each other. The Sox ended a nearly century long championship drought after coming back from a 3 games to 0 play off series deficit by winning 4 straight games in the 2004 playoffs.These are two frequently good teams in two baseball crazy towns whose games against each other are often high drama. Of course the rivalry is often about the fans more than the players. However it is great for the fans and great for the game.