Most sources agree that, adjusting for inflation, John D. Rockefeller (1839–1937) was the richest man in the United States.[1][2][3]
There are various methods of comparing individuals' wealth across time, including using simple inflation-adjusted totals or calculating an individual's wealth as a share of contemporary gross domestic product (GDP). For example, economic blogger Scott Sumner noted in 2018 that Rockefeller was worth $1.4 billion when he died in 1937, about $24 billion in dollars adjusted to 2018. Meanwhile, Bill Gates in 1999 was worth nearly $150 billion in dollars adjusted to 2018.[4]
The second-richest person in terms of wealth compared to contemporary GDP is a subject of dispute. While most sources attribute this status to Andrew Carnegie, others argue that it could be Bill Gates, Cornelius Vanderbilt I, John Jacob Astor IV, or Henry Ford. Determining the lower ranks is an even more contentious debate. Vanderbilt left a fortune worth $100 million upon his death in 1877, equivalent to $2.4 billion today.[5] As the United States became the world's leading economic power by the late 19th century, the wealthiest people in America were often also the wealthiest people in the world.