Comparing wealth of individuals across large spans of time is difficult, as the value of money and assets is heavily dependent on the time period. 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 this reason, there is not one decisive ranking of the richest Americans in history. Many sources cite John D. Rockefeller (1839–1937) as the richest person in the history of the United States, however this result comes not from adjusting his wealth for inflation, but by comparing his wealth to the size of the American economy at that time. Since the economy was relatively small during his time period, his wealth represented a larger portion of the total economy. For example, economic blogger Scott Sumner noted in 2018 that Rockefeller was worth $1.4 billion when he died in 1937, equivalent to about $24 billion in dollars in 2018 when adjusting for inflation. Meanwhile, Bill Gates in 1999 was worth nearly $150 billion in dollars adjusted to 2018. 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. 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.

Fortune's wealthiest Americans (1957)

In 1957, Fortune magazine developed a list of the seventy-six wealthiest Americans, which was published in many American newspapers. Jean Paul Getty, when asked his reaction to being named wealthiest American and whether he was worth a billion dollars, said, "You know, if you can count your money, you don't have a billion dollars" and then added, "But remember, a billion dollars isn't worth what it used to be." The second category, the second to eighth richest individuals, included Andrew Mellon's son, daughter, niece, and nephew. Wealthiest Americans included a total of seven members of the Rockefeller family, five members of the Ford family, four members of the Du Pont family (and a non-family DuPont executive), and four General Motors executives.

$400,000,000 to $700,000,000

$200,000,000 to $400,000,000

$100,000,000 to $200,000,000

$75,000,000 to $100,000,000

Klepper and Gunther (1996)

In the 1996 book The Wealthy 100, authors Michael Klepper and Robert Gunther placed John D. Rockefeller atop the list of the richest Americans in history, followed by Cornelius Vanderbilt and John Jacob Astor. Bill Gates was the top living person, coming in fifth.

American Heritage (1998)

American Heritage magazine published the following list of 40 richest Americans ever in 1998, subtitling it "Surprise: Only three of them are alive today". The list was compiled by taking each person's wealth at death, adding the amount given away during his lifetime, and expressing the total as a fraction of the nation's GDP at the time.

Bernstein and Swan (2008)

Bernstein and Swan in All the Money in the World (2008) mention the 15 richest Americans in history.

Business Insider (2011)

Business Insider agreed on Rockefeller in first, but placed Andrew Carnegie second, followed by Vanderbilt, and Gates.

CNN Money (2014)

The following is a list compiled by CNN Money in 2014.

By half decade

This list names the richest American by half decade starting in 1770.