How many World Series have seen Game 7 go to extra innings?

How many World Series have seen Game 7 go to extra innings?

The 2016 Cubs/Indians World Series was the 4th time.(Although in 1912 game 8 went extra innings-see below for more info on that)

World Series extra-innings in game 7
• 1924 Washington def N.Y. Giants 4-3 in 12
• 1991 Minnesota def Atlanta 1-0 in 10
• 1997 Florida beat Cleveland 3-2 in 11
• 2016 Cubs def Indians 8-7 in 10

*55 extra-inning games have been played in World Series history.

Source for above:  World Series extra-inning games:

Interesting fact: I was looking up world series game 7’s with extra innings and noticed in 1912 game 8 went to extra innings. 1912 was one of only four World Series to go to eight games, and the only best-of-seven Series to do so. While the 1912 Series was extended to eight games due to a tie game being called on account of darkness, the 1903, 1919, and 1921 World Series were all best-of-nine affairs that happened to run eight games.