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.

The Travelers Life & Annuity building in New York. Reuters

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

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.

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.

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.

Cit Group logo
CIT Group logo CIT Group

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

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.

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.

The Facebook logo behind a silhouette. Reuters

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

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.