Pakenham, Sir Richard (1797–1868), diplomat, was born 19 May 1797 at Pakenham Hall, Castlepollard, Co. Westmeath, fifth son of Admiral Sir Thomas Pakenham and Louisa Anne Pakenham (née Staples), granddaughter of William Conolly of Castletown, Co. Kildare. He was the nephew of Edward Michael Pakenham, 2nd Baron Longford, and the cousin of Maj.-gen. Sir Edward Pakenham (qv), killed commanding the British force at the battle of New Orleans (1815). Pakenham was educated at TCD. On 15 October 1817 he entered the British foreign service as an attaché at The Hague in the employ of his uncle, Richard Le Poer Trench (qv), 2nd earl of Clancarty. He was secretary to the British legation in Switzerland, beginning 26 January 1824, and in Mexico, beginning 29 December 1826. On 12 March 1835 Pakenham was appointed British minister to Mexico, where in 1839 he successfully facilitated a rapprochement between Mexico and France, and in 1841 negotiated a treaty supporting an end to the international slave trade. Returning to England in 1843, he was made a privy councillor (13 December) and appointed minister to the United States (14 December). Pakenham was unable to prevent the American annexation of the Republic of Texas, a former province of Mexico. He was authorised to settle the British–American boundary of the Oregon territory, which had troubled diplomatic relations for decades. Although instructed to accept a compromise boundary along the 49th parallel of latitude, he rejected an American proposal, precipitating a crisis that led to preparations for war. Only after considerable private negotiation was a British proposal accepted by the US senate and subsequently by President James K. Polk, resulting in a treaty signed on 15 June 1846. Pakenham returned to England in 1847, and was made a KCB in 1848. He was appointed minister to Portugal on 28 April 1851. Although returning to England in May of 1855 with the intention of retiring, Pakenham was sent back to Lisbon on a special mission in August to extend congratulations to Pedro V. He returned in October, retiring with a diplomatic pension to Coolure, Castle Pollard, Co. Westmeath, where he died on 28 October 1868. There is no known collection of his private correspondence; diplomatic correspondence may be found at the National Archives, Kew, in FO 50 (Mexico), FO 5 (United States), and FO 63 (Portugal).
DNB; James J. Barnes and Patience P. Barnes, ‘Sir Richard Pakenham and the Oregon question, 1843–1846’, Private and confidential: letters from British ministers in Washington to the foreign secretary in London, 1844–67 (1993), 21–37