After Boston had won the American League championship in 1903 and Pittsburgh had prevailed in the National circuit, the presidents of these clubs, Matt Killilea (Boston) and Barney Dreyfuss (Pittsburgh) agreed to a post-season meeting of their clubs. A nine game series was scheduled; the first team to win five to be declared the winner.

The example set by the champions of their leagues, other clubs quickly followed their lead. Post-season confrontations were arranged between the two Philadelphia clubs; the two in St. Louis; the Chicago rivals; and even a series between Cincinnati of the NL and Cleveland of the AL for the championship of Ohio.

In subsequent years meetings for a city or state championship were repeated sporadically but only the Chicago series persisted with some degree of regularity. Through 1942 a total of 26 City Series were contested in Chicago from that 1903 inaugural. The dominance of the White Sox in these autumn affairs defies logic; the Chicago Americans triumphed 19 times while the Nationals could claim Chicago championships on only six occasions; the first series ended in a tie. In the years between 1903 and 1942 a total of 161 games were played with the White Sox winning 95 times and the Cubs taking 62 games. Four of the games ended in deadlocks.