John D Rockefeller was the world's first billionaire, who rose to this status in 1916, when rising share prices pushed his fortune beyond $1 billion. Rockefeller founded Standard Oil in 1870, and by the late 1880s, it controlled about 90% of US refining. $1 billion in 1916 had the purchasing power of roughly $30.5 billion in 2026 (adjusted for inflation).