With two college dropouts, several graduates of state universities and, not surprisingly, some Ivy Leaguers, America's biggest billionaires are a diverse group indeed. Here are the undergraduate and graduate degrees that helped our wealthiest citizens get to the top of the heap. Learn more about an online M.B.A. degree.

1) William H. Gates III

• Estimated Wealth: $56 billion
• Source of Wealth: Founded Microsoft
• America’s most famous college dropout, Gates attended Harvard University until his junior year, when he left to run a company he had already started called Microsoft with childhood friend Paul Allen. Father an attorney, mother a schoolteacher.

2) Warren Buffett

• $51 billion
• Founder of capital management firm Buffett Partnership, which later became Berkshire Hathaway, which now owns controlling stakes in Geico, Dairy Queen, Borsheim’s Jewelry, Mid-American Energy and owns large stakes in Coca Cola and Wells Fargo.
• Attended undergraduate classes at Wharton Business School for two years, but left because he felt he knew more than the professors. Finished bachelor of arts and science degree at University of Nebraska, Lincoln, and then applied to Harvard for graduate business study. Rejected by Harvard, he attended Columbia Business School, where he received a master’s degree in economics.

3) Lawrence Ellison

• $25 billion
• Founder of database company Oracle
• Born to an unwed mother in Bronx, NY, Ellison was given to a great aunt and uncle in Chicago who raised him. Never a fan of academics, he attended University of Illinois at Urbana, Champaign but left at the end of his second year without taking his exams due to the death of his adoptive great aunt. Then attended University of Chicago for one term, where he first became involved in computers. Moved to California without completing any degree program, where he worked for various tech companies before starting Oracle.

4-7) Heirs of Sam Walton
Source of Wealth: Father Sam Walton (1918-1992) founded Wal-Mart (Sam Walton earned bachelor’s degree in economics from University of Missouri, Columbia).

Jim Walton

• $23 billion
• Bachelor of arts and science degree, University of Arkansas.

Christy Walton

• $22 billion
• Widow of Wal-Mart heir John Walton, who attended College of Wooster in Wooster, Ohio (small Presbyterian liberal arts school picked by his mother). He left before completing his degree to go to Vietnam as Green Beret.
• No education information available on his widow Christy Walton.

S. Robson Walton

• $23 billion
• Attended College of Wooster, but transferred after two years to the University of Arkansas in Fayetteville, where he earned bachelor of science degree in business administration. Then got a juris doctor degree from Columbia Law School in New York.

Alice Walton

• $23 billion
• Earned bachelor of arts degree in economics and finance from Trinity College in San Antonio, Texas. Worked briefly as a broker for E.F. Hutton and later founded investment firm Arvest.

8) Michael Bloomberg

• $20 billion
• Founder of financial data and news supplier Bloomberg LLP
• Bachelor of science degree in engineering, Johns Hopkins University; M.B.A. Harvard University.

9) Charles Koch

• $18 billion
• Owner, with his brother David, of conglomerate Koch Industries, which owns business lines in energy, chemical technology, fertilizer, fibers and polymers and other areas.
• Bachelor of arts from Massachusetts Institute of Technology in science; master of science degree in nuclear and chemical engineering.

10) David Koch

• $18 billion
• Bachelor of arts in science from Massachusetts Institute of Technology; Master of science degree in chemical engineering from Massachusetts Institute of Technology.