John Rennie was born in East Linton, Scotland, in 1761. After working as a millwright with Andrew Meikle he studied at Edinburgh University (1780-83).
Rennie was employed by Boulton & Watt for five years but in 1791 he moved to London where he started his own engineering company. Over the next few years he became a famous bridge-builder. This included Leeds Bridge, Southwark Bridge and Waterloo Bridge.
Rennie was also responsible for designing and building docks at Hull, Liverpool, Greenock and Leith and improving the harbours and dockyards at Portsmouth, Chatham and Plymouth. Rennie's last project was London Bridge but it was unfinished when he died in 1821. The bridge was completed by his son, John Rennie.