Kennedy, John Pitt (1796–1879), army officer and agriculturist, was born 8 May 1796 at Donagh, Co. Donegal, fourth son of John Pitt Kennedy, rector of Donagh and later Balteagh, Co. Londonderry, and Mary Kennedy (née Cary). Educated at the Foyle Academy, Derry, he entered the Royal Military Academy, Woolwich, in November 1811 and was commissioned as second lieutenant in the Royal Engineers (September 1815). He was initially employed on the ordnance survey before being posted (1819) to Malta, where he became director of public works at Santa Maura (April 1820). Promoted to lieutenant in June 1821, he was put on half-pay in May of the following year. In 1822 he went to Cephalonia as director of public works and secretary to the island's military governor, Maj. (later Gen. Sir) Charles Napier. Except for a period spent in Woolwich (April–May 1826), he remained in Cephalonia until 1831 and was appointed sub-inspector of militia of the Ionian Islands (January 1828–March 1831). He then returned to Ireland and became an estate manager in Co. Tyrone.
Kennedy had progressive views and felt that the amount of land in Ireland being used for agriculture could be increased. He decided to try to teach Irish farmers new agricultural methods and was a leading exponent of the concept of ‘model’ farms. In 1833 he attended agricultural schools in Germany, Switzerland, and Belgium, and in 1835 he sold out of the army to devote himself to promoting agricultural improvements. In November 1837 he was appointed inspector general of national education and founded a model farm on sixty acres at Glasnevin, Co. Dublin, which he used as an agricultural college. He intended to set up further agricultural colleges in various districts around Ireland but, finding his plans constantly opposed, resigned in March 1839.
In 1843 he was appointed secretary of the Devon commission, in 1845 he became secretary of the famine relief committee, and in 1846 served as a superintendent of relief works in Co. Limerick. As the likelihood of some form of uprising became more of a certainty in early 1848, he offered his assistance in organising the defences of Dublin. Placed in command of volunteer forces, he planned to defend the city by securing key strategic points in Dublin. He also suggested that Dublin Orangemen be armed but the lord lieutenant, Lord Clarendon (qv), quashed this idea. On his own authority he supplied the Orangemen with weapons; his actions were later criticised in the commons but defended by Clarendon.
Reinstated in the army in March 1849, Kennedy served as military secretary to Sir Charles Napier in India (1849–52) and took part in the expedition to Peshawar and in the relief of Kohat. He was also responsible for several works of engineering in India, including the military road that runs from Simla to the border of Tibet. This road was later named after him. In November 1850 he was appointed consulting engineer by the government of India for railroads and drew up the plans for the railway system in India. Returning to England, due to ill health, in 1852, he was promoted lieutenant-colonel in June 1853, retiring on half-pay in November of the same year. He was a founder, and then managing director, of the Bombay, Baroda & Central Indian Railway and returned to India to survey the line in September 1853. A further trip to India followed, again on railway business (1863), and he was elected a member of the Institution of Civil Engineers in March 1868. He wrote numerous works during his career on economic, engineering and social topics including Instruct, employ; don't hang them, or Ireland tranquillised without soldiers and enriched without English capital (London, 1835), Analysis of projects proposed for the relief of the poor of Ireland (London and Dublin, 1837) and Report addressed to the railway proprietors of Great Britain and Ireland (London, 1849). He died at his London residence, St George's Square, 28 June 1879.
He married (October 1838), in Dublin, Anna Maria (d. 1902), eldest daughter of Charles Style, of Glenmore, Stranorlar, Co. Donegal. They had three sons and one daughter; one son and his daughter survived him.