Clinching a playoff spot can happen in a variety of ways. As a fan, it's always best to watch your team clinch a playoff berth with a victory at home, but it actually happens that way less often than usual.
In both 2015 and 2016, the Cubs earned their playoff berth with opponent losses. I looked at all of the Cubs postseason clinching games going back to 1906 and here are my top 5 favorites, with a few honorable mentions and the other Cubs clinchers since 1906.
September 27, 2003: Cubs sweep a doubleheader against the Pirates to clinch the NL Central title.
September 19, 1906: Cubs win their 106th game of the season on their way to a record 116 win season.
October 2, 1910: Cubs clinch the pennant and turn a triple play in the same game!!
September 23, 1907: Cubs clinch the pennant for a trip to World Series and 3 Finger Brown gets his 20th win of the season.
August 29, 1918
The 1918 season was cut short when the United States entered the war.
At Weeghman Park, the Cubs clinched the NL pennant to advance to the World Series with a doubleheader sweep over the Reds. In game 1, Cubs pitcher lefty Tyler won his 18th game of the year pitching a 5-hit, complete game shutout in the Cubs 1-0 victory. Cubs win 2nd game of doubleheader 6-4.
September 18, 1929
Giants 7 Cubs 3 at Wrigley Field
Pirates loss to the Braves clinches NL Pennant for Cubs.
September 20, 1932
Cubs 5 Pirates 2 GM1 of Doubleheader at Wrigley Field.
October 1, 1938
Cubs 10 Cardinals 3 in St. Louis, 2nd game of Doubleheader
Septmeber 29, 1945
Cubs 4 Pirates 3 in GM1 of a Doubleheader
Hank Borowy gets victory.
September 28 2007
Carlos Zambrano helps Cubs shut out the Reds 6-0 in Cinncinnatti. Alfonso Soriano gets the Cubs off to a great start with his 6th leadoff the game home run in the month of September.
September 20, 2008
Cubs 5 Cardinals 4 at Wrigley Field.
Ted Lilly 16th win, Kerry Wood 32nd save
September 25, 2015
Pirates 3 Cubs 2 at Wrigley Field
Giants loss clinches playoff berth for Cubs (they were 2nd wild card team in 2015)
September 15, 2016
Brewers 5 Cubs 4
Cardinals loss to Giants clinches NL Central division and playoff berth for Cubs.