John D. Rockefeller (1839 – 1937)

Measured as a percentage of the overall U.S. economy, Rockefeller's wealth in 2007 dollars would be about $190 billion.

In 1870, at the age of 31, Rockefeller founded Standard Oil of Ohio and rapidly expanded the company by undercutting the competition and then acquiring them. Within a few years, Rockefeller and his partners had a near monopoly on oil refining and marketing in the United States, consolidating their holdings under the Standard Oil Trust.

The Trust's aggressive business practices became a constant target of journalists and the government, and in 1911 the Supreme Court ruled that the company was in violation of the Sherman Antitrust Act. It was broken up into 34 companies, including what are now ConocoPhillips, ExxonMobil, Chevron and Amoco.

As a philanthropist, Rockefeller gave away tens of millions of dollars to a variety of causes. His contributions helped fund Spellman College, an African-American women's school in Atlanta, as well as the University of Chicago and Rockefeller University in New York.

BIO

BORN: July 8, 1839, Richford, N.Y.

DIED: May 23, 1937, Ormond Beach, Fla.

NOTE: The New York Times obituary wrote: "Starting life as a poor boy in an office ... he became the pioneer of efficient business organization and of the modern corporation, the most powerful capitalist of his age, and the greatest philanthropist and patron of higher eduction, scientific research and public health in the history of the world."

Photo Credit: Caricatures by Currier & Ives

Commodore Cornelius Vanderbilt (1794 – 1877)

Measured as a percentage of the overall U.S. economy, Vanderbilt's wealth in 2007 dollars would be about $143 billion.

A relentless -- and some would say ruthless -- competitor, Vanderbilt got his start at the age of 11 working on ferries around New York. By the time he was 16 he was operating his own schooners, ferrying freight and passengers across New York Bay and acquiring the title "commodore."

In 1818, Vanderbilt turned to steamships, and it wasn't long before he was encroaching on a monopoly that Robert Fulton and Robert Livingston had secured from the New York Legislature, leading to a lawsuit that went before the Supreme Court.

By the 1840s, Vanderbilt had a steamship empire. But it wasn't until the 1860s that Vanderbilt began investing in railroads, which earned him the bulk of his fabled fortune.

BIO

BORN: May 27, 1794, Staten Island, N.Y.

DIED: Jan. 4, 1877, New York

NOTE: To establish Vanderbilt University, Vanderbilt gave $1 million, the largest charitable gift in U.S. history to that date.

Painting by Gilbert Stuart

John Jacob Astor (1763 – 1848)

Measured as a percentage of the overall U.S. economy, Astor's wealth in today's dollars would be about $116 billion.

It was an encounter with a fellow passenger sailing to the United States in 1784 that opened Astor's eyes to the money that could be made by buying furs from indians and frontiersmen and selling them to dealers. By 1786, after brief employment with an established furrier, Astor opened a shop in New York. By 1800 he had amassed a fortune of $250,000 and a was expanding his business to the West Coast of North America, Europe and China.

Born in Germany, Astor learned English in London before sailing to the United States. He capitalized on a new U.S.-England treaty to move into markets that had previously been closed. Astor's investments in New York real estate, however, are the source of most of the family's vast fortune. Among his many gifts, Astor gave $400,000 for the development of a library in New York.

BIO

BORN: July 17, 1763, Waldorf, Germany

DIED: March 29, 1848, New York

NOTE: Astor was a financial patron of John James Audubon, Edgar Allan Poe and presidential candidate Henry Clay.

Library of Congress

Stephen Girard (1750 – 1831)

Measured as a percentage of the overall U.S. economy, Girard's wealth in 2007 dollars would be about $83 billion.

French-born Girard first went to sea at age 14 and within a decade was commanding a ship that was conducting trade between the coastal communities of North America and the West Indies. British blockades during the American Revolutionary War hampered his trading career, but Girard picked it back up after the war, building a global shipping business that became the foundation of his wealth.

Girard's banking interests, however, are what catapulted him into the highest echelons of wealth. He is best known for his purchase of government bonds during the War of 1812, which was largely responsible for financing the war. Childless, Girard left nearly his entire fortune to social welfare institutions.

BIO

BORN: May 20, 1750, Bordeaux, France

DIED: Dec. 26, 1831, Philadelphia

NOTE: In his will, Girard allocated millions of dollars to build and operate a boarding school for "poor, white, male orphans," creating Girard College.

Kees de Vos

Bill Gates (born 1955)

Measured as a percentage of the overall U.S. economy, Gates' wealth is about $80 billion.

At age 13, Gates wrote his first software program, launching a lifelong passion. During his junior year at Harvard, Gates dropped out to work with his hometown friend Paul Allen and form Microsoft. The company's first big break was licensing its MS-DOS operating system to IBM, providing Microsoft with what amounted to an iron grip on the personal computer industry that would last for decades.

As the largest shareholder of Microsoft, Gates became a billionaire by 1983 at the age of 31 and the world's richest man a few years later. In recent years, Gates has largely withdrawn from the day-to-day management of Microsoft to focus his attention on philanthropy through the Bill and Melinda Gates Foundation, a charitable organization he formed with his wife.

BIO

BORN: Oct. 28, 1955, Seattle

NOTE: The Bill and Melinda Gates Foundation was created in 1994 with an initial stock gift of $94 million. It is the largest private foundation in the world.