Dongan (D'Unguent), Thomas (1634–1715), 2nd earl of Limerick , soldier and first governor of New York, was third son of Sir John Dongan, baronet, of Castletown Kildrought (Celbridge), Co. Kildare, and his wife Mary, daughter of Sir William Talbot, baronet, of Carton, and niece of Peter Talbot (qv), archbishop of Dublin, and Richard Talbot (qv), earl of Tyrconnell. After the execution of Charles I his father fled to France; there the young Thomas obtained a commission as colonel in the French army, where his name was usually spelt D'Unguent. He participated in Turenne's campaigns against Spain, where he first made the acquaintance of James, duke of York (later James II (qv)).
Dongan remained in the French service after the restoration and was colonel of an Irish regiment in 1674, a commission worth £5,000 a year. When Charles II in 1677 commanded all his subjects to leave the French service, Dongan's acquiescence displeased Louis XIV, who swiftly banished him from France, thereby forcing him to forgo an outstanding debt of 65,000 livres which the king owed him for recruits and arrears of pay. Charles II rewarded him with a pension of £500 a year (which he never got) and the commission of major-general in the army of Flanders. Unable to take up his posting due to the peace of Nymegen, he became lieutenant-governor of Tangier under the 2nd earl of Inchiquin (qv).
In 1682 he received a vice-admiral's commission and became the first governor of the duke of York's province of New York, probably due to his knowledge of Dutch and French and to the rising influence of Richard Talbot at court. He reached New York on 25 August and immediately set about organising the provincial government. He called the freeholders of the province to an assembly and granted it a charter of liberties, which attempted to make them coequal and independent of the English parliament and included a clause guaranteeing liberty of conscience. Dongan also spearheaded the transformation of New York from the struggling Dutch town of 207 houses (New Amsterdam) into a thriving commercial town. In 1686 he presented it with a charter (‘Dongan's charter’) which has remained the basis of the municipal laws, rights, privileges, public property, and franchise in New York city. This document, housed in the New York Public Library, is the city's most precious documentary possession. He also managed to make peace (1684) between the crown and the five nations of the Iroquois confederacy, bringing them under Charles II's suzerainty, while defending their interests against French aggression. In 1688 he settled a number of Irish on Long Island and along the Hudson river in Dutchess and Columbia counties.
Ignominiously dismissed from his post in 1688, possibly as a result of increasing French influence at court and of James's belief that New York would not need a governor when joined to the dominions of New England, he retired to his estate of Castleton, in Staten Island. He refused offers of employment in England and Ireland from James and Tyrconnell, unlike his eldest brother, William (qv), earl of Limerick, who was attainted for his support for James II, his estates passing to the Williamite commander Ginkel (qv). Dongan returned to America, where he obtained a vessel, the Margaret. On the death of his brother William in 1698 he returned to England to petition for the forfeited estate, having succeeded as 2nd earl of Limerick.
Thomas spent his declining years attempting to retain his ancestral lands. In 1700 the English parliament passed an act of resumption of all grants of the Irish forfeitures and vested them in trustees. He petitioned the English parliament for relief and it finally passed a bill giving him liberty to claim his estate. He was strongly opposed by Henry Westenra and others who had paid Ginkel £8,000 for his grant of the estate. However, he could not collect his sizeable arrears of rent or regain rectory and tithe lands, and he had to reimburse two-thirds of the money to those who had purchased his estate from Ginkel. The resulting financial burdens forced him to sell the estate at Castletown in 1709 to William ‘Speaker’ Conolly (qv), leaving nothing but the empty title.
Dongan was one of the prominent Irish catholic aristocrats who met Fr Ambrose O'Connor, Jacobite agent of the queen dowager Mary of Modena, who had been sent in 1708 on a fact-finding mission on behalf of the young Stuart claimant (the Old Pretender). Although more than willing to stress his loyalty to the cause, he urged O'Callaghan not to draw protestant suspicion on himself or his fellow aristocrats.
He died 14 December 1715 and was buried in St Pancras graveyard, London. Survived by his wife Mary (d. 18 November 1720; buried in St James's, Westminster), he bequeathed his New York property in Broadway to his nephews Thomas, John, and Walter Dongan, sons of his brother Col. Michael. The earldom became extinct after his death. His portrait is in the possession of the New York Historical Society.