Half brother to St Leger winner Theodore (b c 1819 Woful) Blacklock was bred at York by Mr Kirby and sold to Richard Watt of Bishop Burton in 1815. The Druid noted that Mr Reed "had the offer of Blacklock for £50; but he neither liked his forelegs nor the recollection of his dam when he saw her crawling past his windows, in York, on her way to the stables of Mr Moss, who had bought her for £3." Blacklock was described by a contemporary turf writer as "a queer-shaped beast, with an enormous fiddle head, but he certainly could gallop." The Druid recollected a conversation with Tom Peirse (whose father William Peirse trained Blacklock): The famous mare, The Duchess, by Cardinal York, led Blacklock in most of his exercise gallops; and, on one occasion, Tom Peirse exclaimed, in his anguish, when he saw the great half-moon head and seven-league stride of Blacklock at work, "Father's going to kill the mare with that half-thick of a horse."

In Mr Watt's stud his success will be ever remembered in the tail male descent: Blacklock - Voltaire - Voltigeur - Vedette - Galopin - St Simon. Among his sons were Chester Cup winner and stallion Brutandorf (b c 1821), Doncaster Cup winner Laurel (br c 1824), York Gold Cup winner and stallion Velocipede (ch c 1825), Tranby (br c 1826) and Belshazzar (ch c 1830) successful stallions in America, and Doncaster Cup winner Voltaire (br c 1826).

He was Champion Sire in 1829. Blacklock died at Bishop Burton in 1831.