National Geographic has a nice article with the largest power outages is the world.
Pictures: World’s Worst Power Outages
Northeastern U.S. and Canada, 1965
Photograph by Bob Gomel, Time Life Pictures/Getty Images
A full moon created an eerie skyline silhouette after New York City went dark during the blackout of November 1965. In a world that's increasingly dependent on constant power, massive electrical outages are a common concern and may strike systems across the globe.
Gets you thinking about how the local data centers weathered the outages.