Nimmo, Alexander (1783–1832), civil engineer, was born in Kirkcaldy, Fifeshire, Scotland, son of Alexander Nimmo, watchmaker and merchant; nothing is known of his mother. He was educated at the universities of St Andrews and Edinburgh, where he gained distinctions in classics and mathematics, and was subsequently appointed schoolmaster and rector of Inverness Academy (1802). On the recommendation of Thomas Telford he conducted a survey in 1806 for a parliamentary commission to define the Scottish county boundaries, and in 1811 resigned his teaching position to engage full-time on surveying and engineering projects.
That year he moved to Ireland, where he was to spend a considerable part of his working life engaged in public works. He joined the Irish bog commissioners as a surveyor, and for much of the next decade traversed many areas in the western part of Ireland mapping bogs; his account of this work was published in 1814. He followed this work with a visit to the Continent, a trip undertaken to examine various public works, before returning to Ireland where he worked as an engineer for the office of public works. In addition he also prepared navigation charts of Ireland's coasts, designed over thirty harbours, and surveyed many others for the Irish fishery board. Part of the docks in Galway city are known as Nimmo's Pier. He built roads and bridges, including a fine single-span bridge of 65 ft (20 m) over the waterfall at Poulaphuca, Co. Dublin (1828), and another crossing the River Shannon at Limerick (1835). He built the village of Roundstone in Co. Galway (1822) and settled Scottish fishermen there, and was also responsible for laying out the village of Knightstown on Valentia Island, Co. Kerry, for the knight of Kerry, who wished to provide adequate housing for workers in his local slate quarry. Nimmo was also the consulting engineer to the duchy of Lancashire, and was the engineer for various railway lines in north-west England, including the Liverpool–Leeds railway.
Nimmo was well versed in modern languages as well as in science. Much of his written legacy is to be found in various official reports on public works for parliament; he also contributed articles to Brewster's cyclopedæia on inland navigation, bridges (co-authored with Thomas Telford, his mentor and tutor), and carpentry (co-authored with Peter Nicholson). Apart from engineering, his interests included geology, astronomy, and chemistry, and he was a mathematician of some note. He held membership of several engineering and scientific bodies: the Geological Society (of London) (1809), the Royal Society (1810), the Royal Society of Edinburgh, the RIA, and the Institute of British Engineers.
He never married. He died 20 January 1832 at his house in Dublin, having suffered from rheumatism for some time. His letters are in the BL; his manuscripts relating to bog and harbour surveys, and those from his public works, are in the NLI and NAI respectively, and those pertaining to his work on English railways are in the National Archives (Kew). A bust by John Edward Jones (qv), a former pupil, is in the collections of the RDS.