[5] The aqueduct was designed by civil engineers Thomas Telford and William Jessop for a location near an 18th-century road crossing, Pont Cysyllte.

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.

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

A plaque commemorating its inauguration reads: The nobility and gentry, the adjacent Counties having united their efforts with the great commercial interests of this country.

In creating an intercourse and union between England and North Wales by a navigable communication of the three Rivers, Severne [sic] Dee and Mersey for the mutual benefit of agriculture and trades, caused the first stone of this aqueduct of Pontcysyllty [sic], to be laid on the 25th day of July MDCCXCV [1795].

With the completion of the aqueduct, the next phase of the canal should have been the continuation of the line to Moss Valley, Wrexham where Telford had constructed a feeder reservoir lake in 1796.

The plan to build this section was cancelled in 1798, and the isolated feeder and a stretch of navigation between Ffrwd and a basin in Summerhill was abandoned.

Subsequently, the Plas Kynaston Canal was built to serve industry in the Cefn Mawr and Rhosymedre areas in the 1820s.

[11] Goods traffic was brought down to the canal by the Ruabon Brook Tramway which climbed towards Acrefair and Plas Bennion.

But the intent of the merger was to build railways at a reduced cost, by using the existing routes of the canals they owned.

The flow of hundreds of tons of water washed away the embankment of the railway further down the hill, tearing a 40-yard (37 m) crater 50 feet (15 m) deep.

[14] This caused the first traffic of the morning, a mail and goods train composed of 16 carriages and two vans, to crash into the breach, killing one and injuring two engine crew.

[15] The aqueduct was saved (despite its official closure to waterway traffic) because it was still required as a water feeder for the remainder of the Shropshire Union Canal.

In 1955 the Mid & South East Cheshire Water Board agreed to maintain the canal securing its future.

The Pontcysyllte Aqueduct is now maintained and managed by the Canal & River Trust (branded Glandŵr Cymru in Wales).

[19] The iron castings for the trough were produced at the nearby Plas Kynaston Foundry, Cefn Mawr, which was built by the Shrewsbury ironfounder and millwright William Hazledine in the hope of gaining the contract.

[22][23] As with Telford's Longdon-on-Tern Aqueduct, the plates are not rectangular but shaped as voussoirs, similar to those of a stone arch.

[25] A feature of a canal aqueduct, in contrast with a road or railway viaduct, is that the vertical loading stresses are virtually constant.

Every five years the ends of the aqueduct are closed and a plug in one of the highest spans is opened to drain the canal water into the River Dee below, to allow inspection and maintenance of the trough.

[30] The aqueduct and surrounding lands were submitted to the "tentative list" of properties being considered for UNESCO World Heritage Site status in 1999.