Four years later Paul Mellon presented both the building by John Russell Pope and his father's collection of 115 paintings to the nation.

Beginning in the late 1950s, with the help of English art historian Basil Taylor, Mellon amassed a major collection by the mid-1960s.

London art dealer Geoffrey Agnew once said of his acquisitions: "It took an American collector to make the English look again at their own paintings."

[4] Mellon granted his extensive collection of British art, rare books, and related materials to Yale University in the 1960s, along with the funding to create an appropriate museum to house it (designed by Louis Kahn).

Mellon also provided extensive endowment support to fund not only operations but also an ongoing program of acquisitions, and he made a generous bequest to the Center at the time of his death.

Mellon owned many thoroughbred horses under his Rokeby Stables, including Kentucky Derby winner Sea Hero.

His most generous and well-known gifts established the Yale Center for British Art, but his legacy makes itself felt across the campus.

Designed by Eero Saarinen, these colleges along with the Kahn-designed British Art Center demonstrated Mellon's commitment to bringing modern architecture to Yale.

Perhaps most importantly, the additional undergraduate capacity that these colleges provided were a critical prerequisite to the ability of the university to transition to co-education.

He supported significantly the undergraduate theater studies program, and endowed named professorships in schools throughout the University, particularly in the humanities.

This organization allocates grants towards specific research projects for the safety, welfare, longevity and improvement of life for racehorses.

He donated the $1 million bonus that Sea Hero won in the Chrysler Triple Crown Challenge to the Grayson-Jockey Club Research Foundation.

Indeed, Clare Hall, founded 1966, gains much from his benefaction; his generous bequest serves the intellectual needs of the graduate college members.

The Mellon Fellowship is another example of his generosity, permitting the reciprocal exchange of two students from Yale and two from Clare College for graduate study in each other's institutions.

"It was while I was at Cambridge that I embarked on the dangerous seas of collecting", Paul Mellon once said—a statement by the man who described himself as "the incurable collector" that has had profound implications for his major beneficiaries, both in the US and the UK.

Among honors, he was elected to the American Philosophical Society in 1971,[11] created an Honorary Knight Commander of the Most Excellent Order of the British Empire (KBE) in 1974, awarded the National Medal of Arts in 1985, elected a member of the American Academy of Arts and Sciences in 1992,[12] and awarded the National Humanities Medal in 1997.

After his wife Mary's death in 1946 from an asthma attack, he married Rachel Lambert Lloyd, known as "Bunny", the former wife of Stacy Barcroft Lloyd Jr. She was a descendant of the Lambert family who formulated and marketed Listerine and an heiress to the Warner-Lambert corporate fortune (Warner-Lambert is now part of Pfizer, following a 2000 merger).