It's referring to the fact that Ontario and Quebec were Upper and Lower Canada, and as the country grew, things to the "West" and "East" were seen in that light, even though it doesn't make sense centuries later.

Sports leagues mirror those commmon conceptions. Toronto is always put in the East alignment of pro sports leagues. Apart from a rough patch for the CFL in the 1980s when the Winnipeg Blue Bombers were moved over to the East, they and the Jets have always been in the West.