On the 50th anniversary of the assassination of President John F. Kennedy, TIME proclaimed that his death was “the moment that changed America.” “There is little doubt that his death and its circumstances set loose the darker instincts of the American psyche,” TIME’s editor Nancy Gibbs wrote then.

And, looking back on the 20th century—the epoch that TIME founder Henry Luce dubbed “the American century”—it’s clear that there were many such moments of change, instances big and small that cleared the way for something greater to come after. Many of those moments are easy to name: the assassinations, the invasions, the elections. Many are more subtle, their impact visible only in hindsight.

With that in mind, TIME invited experts to nominate 20th-century moments that changed the United States. Taken together, those moments create a chronology of an evolving country—and a century in which any moment might be the next big one.

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