Thomas Denny Sanford was born on December 23, 1935, in Saint Paul, Minnesota, during the Great Depression. Sanford's mother, Edith, died when he was 4 years old from breast cancer. His first job was at age 8 working in his father's garment shop. In his teenage years, he was arrested for drinking and fighting and placed in a Juvenile detention center, being released after 36 days on the condition that he enroll in college. He became a student at the University of Minnesota, intending to become a Doctor. But he struggled with chemistry and switched majors. At age 20, Sanford's Father passed away. Sanford eventually graduated from the University of Minnesota with a degree in psychology in 1958.
Sanford graduated from the University of Minnesota in 1958 with a degree in psychology. In 2003, Sanford and the University of Minnesota announced that Sanford would donate $35 million towards a proposed new football stadium for the Minnesota Gophers football team; a deal which would have given him full naming rights. However, that deal fell through in late 2003 when the two parties were unable to reach an agreement on terms of the funding. Later in 2005, TCF Bank won the bid to receive naming rights for the new stadium.
BusinessWeek magazine listed him as one of the top-50 most generous Philanthropists in November 2006.
On February 3, 2007, Sanford announced a $400 million gift to Sioux Valley Hospitals and Health System, which renamed itself Sanford Health. Largely because of this gift, Sanford came in third on The Chronicle of Philanthropy "Philanthropy 50: Americans Who Gave the Most in 2007."