Following an acrimonious departure and a brief dip in personal fortunes, he embarked on business of his own, investing in land and banking in Florida.

After graduation, he enrolled in the Massachusetts Institute of Technology, sharing a room with his cousin T. Coleman du Pont.

Though he started in a low position, he eventually became known, according to the Alfred I. du Pont Foundation, as "one of the nation's top powder men.

Alfred was directly engaged with the company and instituted major changes to its operation that resulted in greater efficiency and safety, leading to a boom in business.

[3][10] Du Pont's relationship with his second wife, Mary (Alicia) Heyward Bradford (1875–1920), had already been the subject of family scandal, as family members had remarked on the close relationship of the two even before Alicia Bradford's marriage to du Pont's secretary, George Amory Maddox.

Du Pont's adoption of Bradford's daughter, Alicia Maddox, brought fresh gossip to the family, who largely rallied in support of his first wife, which in turn inspired du Pont to file several lawsuits against family members and friends for slander, all of which were dropped in due time.

[3] The mansion is a five-story, 77-room, 47,000 sq ft (4,400 m2) structure that was designed by renowned architects Carrère and Hastings, who also designed the New York Public Library, New York City's Frick Mansion, and Whitehall, the Henry Flagler Museum in Palm Beach, Florida.

The estate was named after the French town affiliated with his ancestor, Pierre Samuel du Pont de Nemours.

[15] This secret and swift transaction gave Pierre du Pont, 60 percent ownership of DuPont Securities and, thereby, considerable control over the family business.

In 1916, shortly after company shareholders voted to remove Alfred du Pont from its board of directors, the United States District Court found that Pierre du Pont had operated in bad faith, ordering a stockholder vote to determine if the stockholders (aside from those who owned the disputed shares) wished to purchase the disputed shares.

[20] By 1920, Ball was an assistant principal at an elementary school in San Diego, California, and du Pont began courting her, at the same time divesting himself of assets and cutting back on spending.

[6] There, du Pont purchased 58 acres (230,000 m2) of land on the St. Johns River and built a 25-room mansion and landscaped grounds, as well as a berth for the couple's motor yacht.

He personally funded a pension plan program for seniors in Delaware in 1929 and turned his attention to revitalizing Florida after the devastation of a 1926 hurricane and the Great Depression.

du Pont de Nemours and Company, he formed an orchestra that was named the Tankopanicum Musical Club.

The vast majority of his fortune was left in testamentary trust with Jessie named as the principal trustee with complete discretion regarding use of any money, but in reality, she deferred business decisions to her brother, who took control of the assets, which included the large Florida landholdings of the St. Joe Company and industrial interests, including the Florida East Coast Railway.

The Alfred I. duPont Testamentary Trust's sole charitable beneficiary is the Nemours Foundation, which runs children's medical facilities in Delaware and Florida.

Beginning in the 1970s, Delaware's Attorney General sued du Pont's brother-in-law Edward Ball and other trustees of the Nemours Foundation for failing to implement du Pont's mission for his Trust and for diverting its assets away from charitable needs in Delaware to fund Trust operations in Florida.

He is interred, along with his wife and brother-in-law, in a large mausoleum on the grounds of the Alfred I. duPont Hospital for Children, one of the first projects created with his trust.

The World War II Liberty Ship SS Alfred I. Dupont was named in his honor.