Merthyr’s Bridges: The Iron Bridge

In our series looking at the bridges of Merthyr, we come to Merthyr’s most iconic bridge, and indeed one of Merthyr’s most iconic lost structures – the Old Iron Bridge.

The Old Iron Bridge, or the Merthyr Bridge as it was originally called was commissioned by William Crawshay to replace a stone bridge that had been washed away by a flood. This act was not entirely altruistic on the part of Crawshay, as the only other bridge across the River Taff in town was Jackson’s Bridge, which had been built in 1793 by the Dowlais Iron Company.

Watkin George, the principal engineer at the Cyfarthfa Works was tasked with designing the new bridge, and he conceived a structure fabricated with cast iron sections. To span the River Taff, George had to design a bridge that would span between 65 to 70 feet from bank to bank, so single cast iron beams would be impractical, as they were limited to 20-25 feet in length due to the possibility of the iron failing due to the continuous traffic that would use the bridge.

He decided, therefore to build a structure comprising three separate sections between 22 and 24 feet long, the thickness of the iron being one and a quarter inches, and he constructed the bridge as a cantilever, with the two end sections mounted on buttresses built on the banks of the river with a convex central section fixed between them.

Work started on the bridge in the middle of 1799, and was completed by April the following year. The new bridge had an overall length of 64 feet, and was five feet wide.

The bridge was in constant use as the only bridge in the centre of Merthyr until a new bridge – the Ynysgau Bridge, also called the New Iron Bridge, was built next to it in 1880.

The amount of traffic using the bridge can be illustrated in the table below (originally from Merthyr Historian Vol 2, used with the kind permission of The Merthyr Historical Society). Following construction of the new bridge, The Old Iron Bridge was used primarily as a footbridge.

In 1963, the bridge was dismantled as part of the refurbishment and ‘improvement’ of Merthyr. The remains of the bridge – indeed the vast majority of it, now lie gathering dust in a warehouse in Merthyr, and all attempts by local historical groups to have the bridge re-erected somewhere in the town (it can’t be re-erected in its former position as the river has been widened), have failed.

To read a fuller account of the history of the Old Iron Bridge, try to get hold of a copy of Volume 2 of the Merthyr Historian where you will find a marvellous article about the bridge by Leo Davies.