The railway line through Caldicot was built as the broad gauge South Wales Railway in 1850, although the nearest station was at Portskewett, two miles to the east. In 1861 a private siding was opened to serve the Caldicot Iron & Wire Works, from 1880 the Severn Tinplate Works, on what is now the industrial estate on the Sudbrook road, south of the castle. In typical broad gauge fashion, these works lines used two short hand-worked turntables to move wagons between the lines, rather than points.