William Avery Rockefeller, Jr. (May 31, 1841 – June 24, 1922), American financier, was a co-founder with his older brother John D. Rockefeller (of the prominent United States Rockefeller family) ofStandard Oil. He was the son of William Avery Rockefeller, Sr. and Eliza (Davison) Rockefeller.

Early years
Rockefeller was born in Richford, New York, and in 1853 his family moved to Strongsville, Ohio. As a young pupil in public school, he was inspired and motivated by his teacher-mentor, Rufus Osgood Mason, whom Rockefeller later named "A Rockefeller Patron".

Business career
In 1865, he entered the oil business by starting a refinery. In 1867, his older brother (John D. Rockefeller)'s partnership of Rockefeller & Andrews absorbed this refinery. In 1870, that company becameStandard Oil.
William was considered far more personable and receptive man to work with than his more conservative older brother.
However, he was very adept in business matters. Rockefeller served as the company's New York representative until 1911 when Standard Oil of New Jersey was split up by the United States Supreme Court. He also had interests in copper, railways, and public utilities, and built up the National City Bank of New York, now part of Citigroup.
In the late 1890s, Rockefeller joined fellow Standard Oil principal Henry H. Rogers in forming theAmalgamated Copper Mining Company, a holding company that intended to control the copper industry. Rockefeller, along with Henry Rogers, devised a deceptive scheme which made them a profit of $36 million. First, they purchased Anaconda Properties from Marcus Daly for $39 million, with the understanding that the check was to be deposited in the bank and remain there for a definite time (National City Bank was run by Rockefeller's friends). Rogers and Rockefeller then set up a paper organization known as the Amalgamated Copper Mining Company, with their own clerks as dummy directors, saying the company was worth $75 million.
They then had the Amalgamated Copper Company buy Anaconda from them for $75 million in capital stock, which was conveniently printed for the purpose. Then, they borrowed $39 million from the bank using Amalgamated Copper as collateral. They paid back Daly for Anaconda and sold $75 million worth of stock in Amalgamated Copper to the public. They paid back the bank's $39 million and had a profit of $36 million in cash. So, by deceiving Daly, the bank, and the public, Rockefeller and Rogers had made Amalgamated Copper a $36 million profit before the company was even operating.
With help from banker John D. Ryan, Amalgamated acquired two large competitors, and soon controlled all the mines of Butte, Montana, later becoming Anaconda Copper Company, fourth largest company in the world by the late 1920s.

Home and family
In 1886, Rockefeller bought property along the Hudson River from General Lloyd Aspinwall, and turned it into a mansion named "Rockwood Hall". The property was subsequently located within the Rockefeller family estate of "Pocantico", in Westchester County, New York (see Kykuit).
 
Rockefeller married Almira Geraldine Goodsell in 1864. Her sister, Esther Judson Goodsell, was married to Oliver Burr Jennings, who became one of the original stockholders of Standard Oil. Their son William Goodsell Rockefeller married Elsie Stillman, daughter of National City Bank president James Stillman, and they were the parents of James Stillman Rockefeller. He was a member of the Jekyll Island Club (aka The millionaires Club) on Jekyll Island, Georgia along with J. P. Morgan and William Rockefeller among others. In 1906, the couple's vacation home onJekyll Island was completed; nicknamed "Indian Mound", the 25-room "cottage" remained in the family until ordered evacuated in 1942 by the U.S. government;^[1] five years later the entire island was purchased by the state of Georgia, and decades later it was listed on the National Register of Historic Places as Rockefeller Cottage.
William Rockefeller died on June 24, 1922 in Tarrytown, New York. He was interred in the Sleepy Hollow Cemetery, Sleepy Hollow, New York.
The New York Times, in discussing a trust he set up for his born and yet-to-be born great-grandchildren, states that "The original William left a gross estate of $102,000,000 which was reduced to $50,000,000 principally by $30,000,000 of debts and $18,600,000 of inheritance and estate taxes."

Children

1. Lewis Edward Rockefeller (1865–1866)
2. Emma Rockefeller McAlpin (1868–1934) married Dr. David Hunter McAlpin
3. William Goodsell Rockefeller (1870–1922)
4. John Davison Rockefeller II (1872–1877)
5. Percy Avery Rockefeller (1878–1934)
6. Geraldine Rockefeller Dodge (1882–1973) married Marcellus Dodge