Construction of the Pontcysyllte Aqueduct, meant to carry the Llangollen Canal across the River Dee in north east Wales, begins under the supervision of Thomas Telford and William Jessop near the eighteenth-century road crossing, Pont Cysylltau.

After the westerly high-ground route was approved, the original plan was to create a series of locks down both sides of the valley to an embankment that would carry the Ellesmere Canal over the River Dee.

However, after Telford was hired the plan was changed to an aqueduct that would create an uninterrupted waterway straight across the valley.

Despite considerable public skepticism, Telford is confident his construction method will work because he had previously built a cast-iron trough aqueduct—the Longdon-on-Tern Aqueduct on the Shrewsbury Canal.