With his brother George, William Smith (Jr) succeeded his father William in the family printselling business in 1835.
William Smith was a member of the Burlington Fine Arts Club, of which Whistler also was a member until 1867. He became an FSA in 1852.
As agent for the British Museum, Smith bought Sheepshanks' collection of Dutch and Flemish prints, William Coningham's collection of early engravings and several other significant print collections.
He was prominent, with his brother George, in the foundation of the National Portrait Gallery; he was one of the original Trustees and Deputy Chairman in 1858.
He presented his watercolour collection to South Kensington Museum and to the National Gallery of Ireland.
Griffiths, Antony, ' William Smith(1808-1876) and the Rise of Interest in Early Engraving', Landmarks in Printmaking, British Museum, London, 1996, pp. 90-112; Dictionary of National Biography, Oxford, 2004.