After an $8.6 billion acquisition of Beneficial by Household International in 1998, Caspersen ran Knickerbocker Management, a private financial firm overseeing the assets of trusts and foundations.

As a philanthropist, Caspersen donated tens of millions of dollars to the Peddie School, Brown, Harvard, and Drew University, while overseeing the Hodson Trust, which benefitted four institutions in Maryland.

He served as a town commissioner in Jupiter Island, Florida, an exclusive upper-class enclave, for four years, resigning a few weeks before his suicide in September 2009.

[2][5] Caspersen's mother, Freda, was a non-practicing Jew, and his father thought that his sons needed a religious upbringing.

[7][8] In 1972, Caspersen joined the legal department at Beneficial Corporation, a large American consumer finance firm.

[2][9] In 1929, Hodson and Caspersen reorganized the firm as Beneficial Finance Corporation and transformed it into one of the largest consumer loan providers in the United States.

[11][14][15] According to Charles "Sandy" Hance, former senior vice president and general counsel of Beneficial, Caspersen was a "pioneer in second mortgages, which later evolved into home equity loans", and that he "saw this trend developing at a very early stage".

[17][18][19] Before it was developed, local newspapers described the Harbour Island as "an industrial wasteland inhabited by wild pigs" and the only structures as rusted railroad tracks and an unused phosphate facility.

Knickerbocker, a private investment firm that oversaw approximately $1 billion in assets of trusts and foundations, had offices in Gladstone, New Jersey and Hobe Sound, Florida.

[2][9] In 1998, Whitman appointed Caspersen to chair a 15-member advisory panel to recommend future development for Ellis Island, and to a public-private partnership to foster business in the state.

[2][10][24] In 2005, Caspersen sought a seat on the town commission in Jupiter Island, Florida; his platform focused on conservation, limiting development, and burying utility cables.

He surprised his fellow commission members and neighbors by suddenly resigning on August 4, 2009, claiming that he anticipated moving from the community.

Pulitzer Prize-winning journalist and Harvard alumnus Daniel Golden, in a book criticizing the role of privilege and wealth at elite colleges, attributed their admission to the prestigious law school to their father's generosity.

[35][36][37] According to Sports Illustrated, Caspersen, described as "portly and patrician, tall and splendidly erect, with a lot of beef in his jowls" recalled being asked by Queen Elizabeth II at the awards ceremony about his role in driving his team of Holsteiners: "I told her it was to lower the carriage's center of gravity, ... She looked at my midriff and said I was well suited for the job.

[38] Caspersen died on September 7, 2009, in the Shelter Harbor community of Westerly, Rhode Island, from an apparent gunshot wound to the head.

[2] According to law enforcement sources investigating the suicide, Caspersen left a note stating that he "was tired, diminished and in constant pain, and that he did not want to be a burden to his loving family".

[2] A memorial service held on September 15, 2009, at St. Peter's Episcopal Church in Morristown, New Jersey, was attended by 900 friends and relatives.

[2] In the weeks after his death, reports emerged that Caspersen had listed his Westerly, Rhode Island, home for sale for $10.9 million, was facing financial and legal difficulties.

[2] Caspersen had begun to step back from various philanthropic efforts and institutional boards at Harvard, Peddie, and the Hodson Trust.

[9] Eight days after his death in 2009, a New York Times article cited an anonymous source, to report that Caspersen was being investigated by the Internal Revenue Service and was suspected of owing as much as $100 million in back taxes and fines, and facing possible imprisonment.

[2][37][40] Caspersen helped the U.S. Equestrian Team establish a permanent home at Hamilton Farm, the former estate of U.S. Treasury Secretary Nicholas F. Brady in Bedminster, New Jersey.

[22][43] In 1998, he provided funding to build a boathouse to benefit the rowing programs of Peddie and the nearby Lawrenceville School on the north shore of Mercer Lake in West Windsor, New Jersey.

[49][50] Critics attacked Harvard's decision to name the facilities after Caspersen after his alleged tax evasion was made public.

[53][54] The university's Rose Memorial Library houses a collection of books, manuscripts, artifacts and papers of Nebraska-born author Willa Cather (1873–1947) assembled from items given by several donors—including significant contributions by Caspersen and his wife.