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Traders work on the floor of the New York Stock Exchange (NYSE) on Oct. 23. Reuters

Twitter’s much-anticipated initial public offering is less than a day away, and many observers expect it to raise billions. For some context, here is a list of the 10 highest-grossing IPOs in U.S. history.

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Two patients rest at the HCA Day Care Center in Singapore on September 17, 2007. Reuters

10. HCA Holdings Inc. (NYSE:HCA) became the largest private-equity-backed IPO in March 2011, raising $3.8 billion.

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The Travelers Life & Annuity building in New York. Reuters

9. Travelers Companies Inc. (NYSE:TRV) raised $3.9 billion during its March 2002 IPO.

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Stephen Schwarzman, chairman and CEO of the Blackstone Group, attends the annual meeting of the World Economic Forum in Davos on Jan. 24. Reuters

8. The Blackstone Group LP (NYSE:BX) raised $4.1 billion in June 2007.

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ConocoPhillips Chairman and Chief Executive Officer Ryan M. Lance rings the closing bell at the New York Stock Exchange on Feb. 27. Reuters

7. ConocoPhillips (NYSE:COP) raised $4.4 billion in October 1998.

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Traders gather at the post that trades CIT Group Inc., before the opening bell at the New York Stock Exchange. Reuters

6. CIT Group Inc. (NYSE:CIT) raised $4.6 billion in July 2002.

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CIT Group logo CIT Group

5. United Parcel Service Inc. (NYSE:UPS) raised $5.5 billion in its November 1999 IPO.

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The Mondelez International logo Reuters

4. Mondelez International Inc. (NASDAQ:MDLZ), known as Kraft Foods before 2012, raised $8.7 billion in its June 2001 IPO.

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Workers assemble Opel "Insignia" cars inside the assembly hangar of General Motors German unit in Frankfurt. Reuters

3. General Motors Company (NYSE:GM) raised $15.8 billion in November 2010.

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The Facebook logo behind a silhouette. Reuters

2. Facebook Inc. (NASDAQ:FB) in May 2012 raised $16 billion.

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A coffee shop displays signs for Discover, Visa and MasterCard. Reuters

1. Visa Inc. (NYSE:V) in March 2008 raised $17.9 billion, making it the largest IPO in U.S. history.