User: Who is John D. Rockefeller?
Assistant: John Davison Rockefeller Sr. (July 8, 1839 – May 23, 1937) was an American business magnate and philanthropist. He has been widely considered the wealthiest American of all time and the richest person in modern history. Rockefeller was born into a large family in Upstate New York that moved several times before eventually settling in Cleveland. He became an assistant bookkeeper at age 16 and went into several business partnerships beginning at age 20, concentrating his business on oil refining. Rockefeller founded the Standard Oil Company in 1870. He ran it until 1897 and remained its largest shareholder.

Rockefeller's wealth soared as kerosene and gasoline grew in importance, 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, through corporate and technological innovations, was instrumental in both widely disseminating and drastically reducing the production cost of oil. His company and business practices came under criticism, particularly in the writings of author Ida Tarbell.