Keegan, John (1813–93), surveyor and diarist, was born at Laragh, near Horseleap, Co. Westmeath, in 1813, the only son of Thomas Keegan (1789–1854), a farmer, and his wife, Mary (née Gannon). The Keegans were descended from the hereditary brehons of the Irish midlands; one ancestor, Murtagh Keegan (b. c.1625), lost lands near Moate, Co. Westmeath, in consequence of the rebellion of 1641, and, being an ‘innocent papist’, recovered them in 1663, but they were forfeited for ever in the 1690s. Thady Keegan, Thomas's father, took in 1765 the lease of the farm at Laragh where John Keegan was born.
John Keegan started school locally (1820), then, after the family moved to Moate (1824), attended a school at Moyvore, acquiring sufficient education to enable him to join the ordnance survey (1 September 1836) as a civil assistant at a wage of 1s. 2d. (£ 0.06) per day and with the opportunity to travel. At once he began the diary by which he is known. Dissatisfied with his wage – it had risen to 2s. 10d. (£ 0.14) by October 1840 – Keegan had himself transferred in April 1842 to the north of England, where wages were higher. Seeing in the ‘railway mania’ of the mid-1840s an opportunity to better himself further, Keegan became a railway surveyor at a wage of £3 per week (October 1845), but the sudden collapse of the boom and his wife's poor health caused him to return to Ireland in November 1846 and obtain employment with the board of works supervising famine relief schemes in the midlands near his home town. Before long he rejoined the ordnance survey and did many more years’ service. After retiring he worked privately in England and in Ireland.
Keegan's diary gives, besides information on the work of the ordnance survey, a rare view of life among the strong farmer and gentry classes of the Irish midlands, south Leinster, and parts of Munster, through the eyes of a young catholic with local roots. Its detailed descriptions of working-class life in the north of England and remarks on the social position of the old catholic gentry and Irish catholic immigrants add to its value. The diary is of interest also for cameos of men and women Keegan met or observed – among them Daniel O'Connell (qv), Theobald Mathew (qv), Bishop John Murphy (qv), and Patrick Brontë (qv). Its unique worth lies in its being the diary of an Irishman of the skilled artisan class, a practising catholic entirely free of bigotry, and with political and literary interests. Whether the manuscript is extant is not known. The published extracts end with Keegan's work on famine relief. Wallace Clare's (qv) edition, the only source for the diary, does not give complete coverage of the period 1836–47.
John Keegan married (1 July 1841) Elizabeth O'Brien of Mitchelstown, Co. Cork, and with her had at least four children, one of whom, Agnes, was the mother of Wallace Clare, who edited the extracts from early parts of Keegan's diary. Keegan died, aged eighty, on 18 August 1893, while surveying lands for a client; he was buried in the parish of Kilcumreragh, Co. Westmeath.