Its success inspired the widespread use of cast iron as a structural material, and today the bridge is celebrated as a symbol of the Industrial Revolution.

The geography of the deep Ironbridge Gorge, formed by glacial action during the last ice age, meant that there are industrially useful deposits of coal, iron ore, limestone and fire clay present near the surface where they are readily mined, but also that it was difficult to build a bridge across the river at this location.

To cope with the instability of the banks and the need to maintain a navigable channel in the river, a single span iron bridge was proposed by Thomas Farnolls Pritchard.

The Ironbridge Gorge was formed at the end of the last ice age by the overflowing of Lake Lapworth, which resulted in the exposure of useful deposits of resources such as coal, iron ore, fire clay and limestone near the surface where they were readily mined.

[5] The River Severn was used as a key trading route, but it was also a barrier to travel around the deep Ironbridge Gorge, especially between the then important industrial parishes of Broseley and Madeley, the nearest bridge being at Buildwas 2 miles (3.2 km) away.

The use of the river by boat traffic and the steep sides of the gorge meant that any bridge should ideally be of a single span, and sufficiently high to allow tall ships to pass underneath.

[11][12] In 1773, architect Thomas Farnolls Pritchard wrote to his 'iron mad' friend and local ironmaster, John Wilkinson of Broseley, to suggest building a bridge out of cast iron.

[15][16] During the winter of 1773–74, local newspapers advertised a proposal to petition Parliament for leave to construct an iron bridge with a single 120-foot (37 m) span.

It had been drafted by Thomas Addenbrooke, secretary of the trustees, and John Harries, a London barrister,[i] then presented to the House of Commons by Charles Baldwyn, MP for Shropshire.

[20] No satisfactory proposal was made, and the trustees agreed to proceed with Pritchard's design, but there was continued uncertainty about the use of iron, and conditions were set on the cost and duration of the construction.

[21][ii] The site, adjacent to where a ferry had run between Madeley and Benthall, was chosen for its high approaches on each side and the relative solidity of the ground.

[28] The painting shows a moveable wooden scaffold consisting of derrick poles standing in the river bed being used as a crane to position the half-ribs of the bridge, which had been taken to the site by boat from Darby's foundry 500 metres (1,600 ft) downstream.

Using the approach depicted in the painting, a half-size replica of the main section of the bridge was built in 2001 as part of the research for the BBC's Timewatch programme, which was shown the following year.

[28][30] The bridge is to a carpenters' design typically used for wood structures, built from five sectional cast-iron ribs that give a span of 100 feet 6 inches (30.63 m).

[26] Decorative rings and ogees between the structural ribs of the bridge suggest that the final design was Pritchard's, as the same elements appear in a gazebo he rebuilt.

This is immensely strong in compression, but performs less well than steel and wrought iron when subjected to tension or bending moments, because of its brittleness and lower tensile strength.

While the actual cost of the bridge is unknown, contemporary records suggest it was as high as £6,000 (£787,113 in 2023)[iv], and Darby, who was already indebted from other ventures, agreed to cover the excess.

[45][46] In 1800 the trustees commissioned repairs which lasted for several years, which involved the replacement of the stone land arches with wooden ones to relieve pressure on the main span.

[47] In 1812, its construction was described as "very bad" by Charles Hutton, and he predicted that it would not last for long, "though not from any deficiency in the iron-work", but due to cracks that had appeared in the stonework.

"[50] On 24 August 1902, a 30-foot (9.1 m) length of parapet collapsed into the river, and a section of deck plate weighing around 5 long hundredweight (250 kg) fell from the bridge in July 1903.

[53] A weight limit of 4 tons was imposed, but the housing boom of the 1930s meant that drivers distributing tiles produced at Jackfield were insistent that they should be allowed to use the bridge, so the trustees took the decision to close it to vehicular traffic with effect from 18 June 1934.

[55][56] The consulting engineers Sandford, Fawcett, Wilton and Bell decided to place a ferro-concrete inverted arch under the river to counter inward movement of the bridge abutments.

[80] An engraving by Michael Angelo Rooker proved popular, and a copy was purchased by Thomas Jefferson where it was displayed in the dining room of Monticello.