[bn2cardz]

I would direct you to this thread:

http://www.net54baseball.com/showthread.php?t=79905

Here is the exact quote pertaining to your question:

Originally Posted by Archive

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As mentioned earlier, there are ten teams included in the set. Five are from the National League (Boston, Brooklyn, New York, Pittsburgh, St. Louis) and five from the American League (Cleveland, Detroit, New York, St. Louis, Washington). Why the other six major league teams (Boston AL, Chicago AL, Chicago NL, Cincinnati, Philadelphia Al, Philadelphia NL) are not included is unknown. The Philadelphia Athletics had won three of the four World Series prior to 1914 and boasted five future HOFers on their roster yet were left out of the set. It has been hypothesized that these cities were not markets for Egyptienne Straights Cigarettes, but this does not explain why members of Boston's NL franchise are in the set while the AL team in the same city is omitted. It is likely we will never know.
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