William was the sixth son of Alexander Cosby (d.1694) of Stradbally, Queen's County (County Laois) and Elizabeth (d.1692), daughter of Henry L'Estrange of Moystown, King's County (County Offaly). Five of William's brothers were also in the armed forces. Cosby himself became a Brigadier General in the army and was Colonel of the Royal Irish Regiment and was eventually appointed Governor of New York and New Jersey.
Cosby lacked statesmanship and was motivated by self-interest. Accusations of violence and profanity, as well as extortion, were made against him and he was thoroughly disliked.
Label TextCosby enjoyed a lengthy military career, becoming a Brigadier General and Colonel of the Royal Irish Regiment. In 1731 he was appointed Governor of New York and New Jersey, but was an unpopular character, accused of violence, profanity and extortion. Here he cuts a confident figure, in a finely detailed velvet military coat and breastplate, his shaved head just visible beneath his bob wig. Jervas was one of the most successful Irish portrait painters of his generation. He was well-connected and possessed considerable business acumen. In 1723, he was appointed Principal Painter to the King.
