Claim: John D. Rockefeller was the richest person in the United States in 1905.

John Davison Rockefeller Sr. -LRB- July 8 , 1839 -- May 23 , 1937 -RRB- was an American oil industry business magnate and philanthropist . He is widely considered the wealthiest American of all time , and the richest person in modern history .   Born into a large family in upstate New York , he was shaped by his con man father and religious mother . His family moved several times before eventually settling in Cleveland , Ohio . Rockefeller became an assistant bookkeeper at the age of 16 , and went into a business partnership with Maurice B. Clark and his brothers at 20 . After buying them out , he and his brother William founded Rockefeller & Andrews with Samuel Andrews . Instead of drilling for oil , he concentrated on refining . In 1867 , Henry Flagler entered the partnership . The Rockefeller , Andrews & Flagler company grew by incorporating local refineries . Rockefeller formally founded the Standard Oil Company , Inc. in 1870 as an Ohio partnership with his brother , Henry Flagler , Jabez A. Bostwick , Samuel Andrews , and a silent partner , Stephen V. Harkness . He ran it until 1897 . As kerosene and gasoline grew in importance , Rockefeller 's wealth soared and he became the richest person in the country , controlling 90 % of all oil in the United States at his peak . Oil was used throughout the country as a light source until the introduction of electricity and as a fuel after the invention of the automobile . Furthermore , Rockefeller gained enormous influence over the railroad industry , which transported his oil around the country . Standard Oil was the first great business trust in the United States . Rockefeller revolutionized the petroleum industry , and along with other key contemporary industrialists such as steel magnate Andrew Carnegie , defined the structure of modern philanthropy .   The U.S. Supreme Court ruled in 1911 that Standard Oil must be dismantled for violation of federal anti-trust laws ; it was broken up into 34 separate entities that included companies that would become ExxonMobil , Chevron , and others ; some of them still having the largest revenue . Individual pieces of the company were worth more than the whole , and as shares of these doubled and tripled in value in their early years , Rockefeller became the country 's first billionaire with a fortune worth nearly 2 percent of the national economy . His peak net worth was estimated at $ 336 billion -LRB- in 2007 USD ; inflation-adjusted -RRB- in 1913 . Rockefeller spent the last 40 years of his life in retirement at his estate in Westchester County , New York . His fortune was mainly used to create the modern systematic approach of targeted philanthropy through the creation of foundations that had a major effect on medicine , education and scientific research . His foundations pioneered the development of medical research and were instrumental in the eradication of hookworm and yellow fever .   Rockefeller was also the founder of both the University of Chicago and Rockefeller University and funded the establishment of Central Philippine University in the Philippines . He was a devout Northern Baptist , and supported many church-based institutions . Rockefeller adhered to total abstinence from alcohol and tobacco throughout his life . He was a faithful congregant of the Erie Street Baptist Mission Church , where he taught Sunday school , and served as a trustee , clerk , and occasional janitor . Religion was a guiding force throughout his life , and Rockefeller believed it to be the source of his success . Rockefeller was also considered a supporter of capitalism based on a perspective of social Darwinism , and was quoted often as saying `` The growth of a large business is merely a survival of the fittest '' .