Lenox went to Europe soon after his admission to the bar, and while abroad, began collecting rare books.
This, along with collecting art, became the absorbing passion of his life.
For half a century, he devoted the greater part of his time and talent to forming a library and gallery of paintings, unsurpassed in value by any other private collection in the New World.
In 1870 these, together with many rare manuscripts, marble busts and statues, mosaics, engravings, and curios, became the Lenox Library in  New York City.
Lenox served as its first president.

The library occupied the crest of the hill on Fifth Avenue, between 70th and 71st Streets, overlooking Central Park.
On May 23, 1895, the Lenox Library was consolidated with the Astor Library and the Tilden Trust to form the New York Public Library.

The collection of Bibles, including the Gutenberg Bible—both in number and rarity—were believed to be unequaled even to those of the British Museum; while its Americana, incunabula, and Shakespeariana, surpassed those of any other American library, public or private.
The collection was valued at nearly a million dollars, which, with the $900,000 for the land, building, and endowment, made the total above $2,000,000.
The Frick Collection stands on the Lenox Library's former site.

Lenox was a founder of the Presbyterian Hospital in New York City.
His gifts to it amounted to $600,000.
He also made important gifts to Princeton College and Seminary, and gave liberally to numerous churches and charities connected with the Presbyterian Church.
Lenox was also the president of the American Bible Society, to which he was a liberal donor.
James Grant Wilson reports passing on several anonymous gifts from Lenox to needy men of letters.
He was elected a member of the American Antiquarian Society in 1854, and served as the society's vice-president from 1868 to 1880.

Lenox occasionally reprinted limited editions, restricted to ten or twenty copies, of rare books, which he placed in some of the great public libraries and notable private collections, for example that of John Carter Brown.
Portraits of Lenox were painted by Francis Grant in 1848, and by G. P. A. Healy three years later.
He was also painted by Daniel Huntington in 1874.
Lenox went to Europe soon after his admission to the bar, and while abroad, began collecting rare books. This, along with collecting art, became the absorbing passion of his life. For half a century, he devoted the greater part of his time and talent to forming a library and gallery of paintings, unsurpassed in value by any other private collection in the New World. In 1870 these, together with many rare manuscripts, marble busts and statues, mosaics, engravings, and curios, became the Lenox Library in  New York City. Lenox served as its first president.
The library occupied the crest of the hill on Fifth Avenue, between 70th and 71st Streets, overlooking Central Park. On May 23, 1895, the Lenox Library was consolidated with the Astor Library and the Tilden Trust to form the New York Public Library.
The collection of Bibles, including the Gutenberg Bible—both in number and rarity—were believed to be unequaled even to those of the British Museum; while its Americana, incunabula, and Shakespeariana, surpassed those of any other American library, public or private. The collection was valued at nearly a million dollars, which, with the $900,000 for the land, building, and endowment, made the total above $2,000,000. The Frick Collection stands on the Lenox Library's former site.
Lenox was a founder of the Presbyterian Hospital in New York City. His gifts to it amounted to $600,000. He also made important gifts to Princeton College and Seminary, and gave liberally to numerous churches and charities connected with the Presbyterian Church. Lenox was also the president of the American Bible Society, to which he was a liberal donor. James Grant Wilson reports passing on several anonymous gifts from Lenox to needy men of letters. He was elected a member of the American Antiquarian Society in 1854, and served as the society's vice-president from 1868 to 1880.
Lenox occasionally reprinted limited editions, restricted to ten or twenty copies, of rare books, which he placed in some of the great public libraries and notable private collections, for example that of John Carter Brown. Portraits of Lenox were painted by Francis Grant in 1848, and by G. P. A. Healy three years later. He was also painted by Daniel Huntington in 1874.
James Lenox