Jan. 15, 2009: As the U.S. Airways jet they had been on sinks into the Hudson River, passengers are rowed away. This isn't the iconic (and now copyrighted) photo that helped transform Twitter. But it does give a sense of what it was like that day, 5 years ago. Bebeto Matthews/AP hide caption

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Twitter made its debut on the New York Stock Exchange in November. Both the social media giant and the relative newcomer Snapchat are valued in the billions, but neither company has yet turned a profit. Emmanuel Dunand/AFP/Getty Images hide caption

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"DOUGH a crust, an unbaked crust ...": Carrie Underwood may have played Maria in NBC's The Sound of Music Live, but on Twitter, it was @DiGiorno that stole the show. NBC/NBCU Photo Bank via Getty Images hide caption

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Twitter announced that it has set a price range for its initial public offering between $17 and $20 per share and hopes to sell 70 million shares. Justin Sullivan/Getty Images hide caption

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