In 1968, 1969 and 1970 for whatever reason they put all the expansion teams in one division and they all played each other en route to the final. This is why there were three sweeps in a row and why great teams like the Habs in 1970 or the Red Wings in 1969 missed the playoffs. 1971 they actually rectified this. Why it took them three years is anybody's guess.
Look how long it took the NHL to expand from 6 teams after having to fold a few franchises. All 6 expansion teams were put in one division because the league wanted them to have a chance to do something. They Bettman'd the league before Bettman did, and that was back when men were men, and losers went home. Maybe if they didn't double the league in one shot they wouldn't have had to do that, but, that was a radical move.
Then when you have 3 sweeps in a row, that's an anti-climactic Final, so move an established team over. Then Philly emerged after a few years, and now there's some competition. Then more expansion teams were added, and they broke up the divisions. They didn't make much sense from a geographical standpoint, but the playoffs weren't geographic anyway. It was league wide, top 3 per division, and division winners got a bye. The Atlanta Flames missed the playoffs in 74-75, despite having a better record than both Chicago and Toronto, because of the playoff format. The more things change...
Geographically speaking, Chicago should've been in the West in 1967 anyway. Them and Detroit. Or, the league could've split into 3 divisions in 1967, with a West, Central, and East, and who knows how that would've changed future alignments. Maybe the league ends up with a MLB/NFL style system. Although it's that way in those leagues because two different leagues merged, not so much an expansion of one league.