Blacklegs was a bay colt bred by William Cavendish, 2nd Duke of Devonshire, and foaled in 1728.
This Basto mare also foaled the champion sire Crab, as well as the previously mentions Snip and Second.
In October 1732 at Newmarket, Blacklock beat the Duke of Bridgewater's Beauty over for mile for 200 guineas.
The following April he won the 700 guineas stakes, beating Sly, Favourite and Quibble over four miles.
He sired several good runners and the dams of Captain, Cassandra, Dorimond, Trajan, Marcus and Jalap.