Margaret Carpenter was born in Salisbury considered to be the most accomplished woman portrait painter of her time, and was a member of an artistic dynasty: her father was the painter Captain Alexander Geddes who was of an Edinburgh family, and Harriet Easton. She was taught art by a local drawing-master. Her first art studies were made from the pictures at Longford Castle, belonging to Lord Radnor.
In 1814 she moved to London and very swiftly established herself as a highly fashionable portrait painter. In 1817, she married William Hookham Carpenter, Keeper of Prints and Drawings at the British Museum. Sarah supplying 236 works for public exhibition at the Royal Academy, the British Institute and the Society of British Artists as well the Suffolk Street Gallery between 1818 and 1866. Among her exhibited portraits were those of Sir H. Bunbury (1822), Lady Denbigh (1831), and Lady King (better known as Ada Lovelace) (1835). Her last work was a portrait of Dr. Whewell. Three of her works are in the National Portrait Gallery, As this portrait demonstrates, her fluid and accomplished manner was most clearly influenced by the work of Sir Thomas Lawrence.
In 1817, she married William Hookham Carpenter, Keeper of Prints and Drawings at the British Museum. Their children included two noted painters, another William and Percy Carpenter, who both travelled. She introduced her sister Harriet to the young painter William Collins. They eventually married, making Margaret the aunt to Wilkie Collins, novelist and friend to Charles Dickens. On her husband’s death in 1866, she was given an annual pension of £100 by Queen Victoria. This award was partly based on her husband’s service, but also in recognition of her own artistic merits. She died in London on 13 November 1872.