On July 10, 1968 — The American League and National League agree on next year’s expansion and playoff format. Each league will divide their twelve teams into two six-team divisions, playing a best-of-five game league championship series to determine the pennant winner.
The National League voted begin divisional play in 1969 with the increase of teams from 10 to 12 with the addition of Montreal and San Diego. The Reds were placed in the Western Division with Atlanta, Houston, Los Angeles, San Diego and San Francisco.
The divisons were in defiance of geographic logic because of Mets chairman of the board M. Donald Grant. The three biggest draws in the NL in 1968 were the Cardinals, Giants and Dodgers, and Grant insisted that the Mets be placed in a division with at least one of them. The Cardinals agreed to go to the East, but only if the rival Cubs would join them.. This put Atlanta and Cincinnati in the west. Reds president Frank Dale expressed satisfaction because the Reds would be in the same divison with the rival Dodgers and Giants.
It proved to be shortsighted on Grant’s part, as the Cards faded to also rans in the 1970s while the Reds became baseball’s biggest draw.