As of March 2026, his net worth was estimated at $2.4 billion, but the South Dakota financial mogul worked tirelessly to shrink that number by pouring funds into healthcare, education, and science. Around $2 billion of that total went to the healthcare system bearing his name, reports Fortune.

“I want to die broke. To put it directly and succinctly, I look at life as an investor: What is going to give me or my community the best return on investment?” he said in a 2007 interview with Forbes.

South Dakota Governor Larry Rhoden called Sanford “the greatest philanthropist in the state’s history.” Thanks to his donations, a modest regional hospital transformed into Sanford Health—one of the largest rural healthcare networks in the United States. Additionally, Sanford funded the Sanford Underground Research Facility, scholarship programs for thousands of students, children’s homes, and charitable foundations.

How Denny Sanford Made His Fortune

Sanford was born into poverty in St. Paul, Minnesota. He lost his mother to breast cancer at age 4 and began working in his father’s clothing shop at age 8. As a teenager, he landed in jail following a street fight, but the judge released him on the condition that he attend the University of Minnesota—a moment Sanford later referred to as the best turning point of his life.

Sanford built his fortune through a niche financial instrument.

In 1986, he acquired a small bank in Sioux Falls, transforming it into First Premier Bank. The bulk of its profits came from its Premier Bankcard unit, which issued high-interest credit cards to customers with poor credit histories. Capitalizing on South Dakota's lax banking laws, Sanford charged customers, for example, a $175 fee for a $1,000 credit limit. He personally described these cards as a “lifeline for people whom nobody else will lend money to.”

The business pushed his net worth beyond $3 billion, after which Sanford made it his primary mission to give every single dollar away during his lifetime. In 2010, he joined the Giving Pledge.

A Shadow Over His Reputation

Despite his sweeping philanthropy, the final years of Sanford’s life were clouded by a high-profile scandal.

In 2020, news broke that the billionaire was under investigation for offenses involving child sexual abuse material (a file was discovered in an email account associated with him). Sanford’s attorneys claimed hacking and stated that third parties had access to his devices. In 2022, the South Dakota Attorney General’s office declined to file charges due to a lack of evidence within state jurisdiction. Nevertheless, in 2023, Sanford was removed from the Giving Pledge list.

Despite the controversies, Sanford went down in U.S. history as one of the most generous benefactors of the 21st century—a man who firmly refused to leave money behind in trusts after his death, choosing instead to fund tangible help while still alive.