During the eighteenth and nineteenth centuries, Great Britain generated spectacular wealth from its colonies. Among the benefits of this wealth was a renewed attention to civil projects--roads, bridges, harbors and, later, railroads. New names to the field of engineering spurred these projects with new ideas.

John Rennie was born in the midst of this renaissance. He became one of several Scottish engineers of the period whose influence was felt throughout Britain and Europe. Rennie was the son of a farmer, and received his education at the University of Edinburgh. When he was only nineteen, he moved to London to begin his career.

Rennie's first significant project was the Albion Flour Mills in London. Completed in 1784, it was the first factory in Britain to be constructed entirely of cast iron. He also made innovative use of machinery in the factory's construction and operation.

From 1804, Rennie worked on the construction of docks in London, Liverpool, Holyhead, Hull, Dublin, and several other ports using masonry and cast iron. He improved and employed steam-powered cranes and dredgers in the construction process. He engineered several major canal projects, including the 78-mile Lancaster Canal at Liverpool, the Rochdale Canal at Manchester, the Kennet, and Avon Canal in the south of England, and the Crinan Canal in western Scotland.

Rennie was best known for his bridges. One of his most famous bridges, the New London Bridge, was composed of multiple masonary arches. The bridge was completed by his son John in 1831, ten years after Rennie's death. It was dismantled in 1970 and reassembled at Lake Havasu City, Arizona. Many of Rennie's bridge projects were closely tied to the new road network of fellow Scottish engineer Thomas Telford. Other bridges of note are the Waterloo Bridge (1817), constructed of granite, and the Southwick Bridge (1819), with its inverted cast iron arches.

Rennie's sons, George and John, went on to follow in their father's footsteps, becoming notable engineers in their own right, George as a mechanical engineer and John as a civil engineer.