John Rennie lived from 7 June 1761 to 4 October 1821. A farmer's son from East Lothian, he went on to become one of the greatest engineers of his age who designed many bridges, canals, and docks. The wider picture in Scotland at the time is set out in our Historical Timeline.
John Rennie was born the fourth son of a wealthy farmer on the Phantassie estate close to the village of East Linton in East Lothian. His father died when Rennie was five. Rennie attended school at Prestonkirk and in Dunbar. In his spare time as a child, Rennie was often at Houston Mill in East Linton, helping Andrew Meikle, a millwright and a famous mechanical engineer who invented (or at least significantly improved) the threshing machine: and so hastened the agricultural revolution. By the age of 10 Rennie had built working models of a windmill, a steam engine, and a pile engine.
In 1777 the schoolmaster at Dunbar took up a new post at Perth Academy and recommended that the 16 year old John Rennie should replace him. Instead, Rennie went to work with Andrew Meikle, building a number of corn mills in East Lothian before he was 18, and a flour mill at Invergowrie near Dundee. From 1780 to 1783 he spent each summer working with Meikle, and the winters studying at Edinburgh University.
In 1783, John Rennie took up a post under James Watt as an engineer at Boulton and Watt's Soho Foundry in Smethwick, near Birmingham. Rennie proved to be expert at substituting cast iron for wood in a wide range of structures. He moved to work at Boulton and Watts' Albion Mills in London in 1789.
Rennie set up his own engineering and civil engineering business in London in 1791. Early projects included the Lancaster Canal (started in 1792), the Chelmer and Blackwater Navigation (started in 1793), the Crinan Canal (started in 1794) and the Kennet and Avon Canal (also started in 1794) along with a drainage scheme for the Norfolk Fens (1802-1810).
He then turned his attention to bridge building, producing stone and cast iron bridges that had unprecedentedly flat and wide arches. These included Leeds Bridge; Waterloo Bridge, Southwark Bridge and London Bridge over the Thames in London; and lesser known bridges in Musselburgh, Kelso and elsewhere.
Rennie's largest works were probably his harbours, and he was responsible for the building of West India Dock, and Blackwall Dock in London; as well as major docks in Hull, Liverpool, Dublin, Greenock and Leith; naval dockyards at Portsmouth, Chatham and Devonport; and lesser harbours at Berwick-upon-Tweed, Dunleary, Howth, Newhaven, and Queensferry. He was also responsible for the building of the Bell Rock Lighthouse between 1807 and 1811, though much of the day to day design was done by Robert Stevenson as was the oversight of the construction.
John Rennie died in London in 1821 and was buried in St Paul's Cathedral. At the time of his death London Bridge was still unfinished, but the work was taken up by one of Rennie's sons, also John Rennie, who as Sir John Rennie went on to be a major force in the railway building boom of the 1800s and was made President of the Institution of Civil Engineers in 1845.