Sloane’s career as a collector really began in 1687 when, as personal physician, he accompanied the new Governor, the Duke of Albermarle, to Jamaica. He collected some 800 species of plants and other live specimens to bring back to London. An account of his travels was published in 1707 and 1725.

In 1742 he moved with his collections to a manor house in Chelsea. His time there is still commemorated by such place names as Sloane Square and Hans Crescent.

Sloane died at the age of 93 in 1753 and was buried at Chelsea Old Church. By then, his collection amounted to more than 71,000 objects. Chiefly natural history specimens, the collection also included:
* 23,000 coins and medals
* 50,000 books, prints and manuscripts
* a herbarium (a collection of dried plants)
* 1,125 'things relating to the customs of ancient times'

In his will, Sloane bequeathed the whole collection to King George II for the nation in return for payment of £20,000 to his heirs.

Parliament accepted the gift and on 7 June 1753 an Act of Parliament establishing the British Museum received the royal assent. Sloane’s collection became the foundation of the British Museum.