The Neath Canal was authorised by an Act of Parliament passed on 6 June 1791, which created The Company and Proprietors of the Neath Canal Navigation. The canal was to run from Abernant to Neath. Thomas Dadford was employed as Engineer, and construction started from Neath, northwards towards Abernant (Glynneath). The canal company completed the building work by 1795.

A second Neath Canal Act was passed on 26 May 1798, to authorise an extension of about 1 mile to Giants Grave, where facilities for transferring goods to sea-going vessels were available. This extension was completed by 1799. Between 1815 and 1842, additional docks and wharfs were build at Giants Grave, extending the length slightly, and the canal was eventually extended to Briton Ferry by the construction of the Jersey Canal in 1842, which was about 1 km (0.6 miles) long. The final length of the canal was 21 km (13.5 miles), with nineteen locks. From the northern terminus, a tramway connected the canal to iron works at Aberdare and Hirwaun. This was built in 1803, and included an incline just north of Glynneath, which was powered by a high-pressure Trevithick steam engine.

The Tennant Canal was built by George Tennant, initially as an extension of the Glan-y-Wern Canal, with the intention of linking the Tawe and Neath rivers. Work started in 1817, under the direction of the engineer William Kirkhouse, and the canal was complete from near the east pier on the River Tawe at Swansea to the River Neath at Red Jacket by 1818. However, barges from the Neath Canal could not cross the river, and so a further extension was started in 1820, to link with the Neath Canal basin at Aberdulais. The extension crosses the river on a ten-arched aqueduct, and the only lock on this section was situated at the south end of the aqueduct. The length of the canal, completed in 1824, was 13 km (8 miles).

At the Swansea end, Tennant built a sea-lock, so that boats could enter Fabian Bay, and named the area Port Tennant. His terminus was destroyed when the Prince of Wales Dock was constructed by the Swansea Harbour Trust in 1881. It occupied all of the area which had been Fabian Bay, and so a lock was constructed so that boats could still reach tidal water by passing through the dock, and a wharf for the canal was constructed at the eastern end of the dock. Tennants wharf was again destroyed in 1898, when the dock was extended. Wharfage was provided for the canal along the entire southern side of the extension, but no lock was built to allow canal boats to enter the dock, even though the act of parliament made provision for one. A new branch of the canal was built in 1909, which included a lock into the newly constructed Kings Dock, where a lay-by berth was provided on its north side.

At Aberdulais the Tennant Canal crossed the river Neath on a ten arch aqueduct which lies parallel to a railway bridge, built in 1851 by Brunel for the Vale of Neath Railway. Originally timber, this was rebuilt in stone in the 1880s.

From Aberdulais a 1 m (3ft 2.5ins) horse tramroad was constructed in 1840 to bring down coal from the Glyncorrwg area on the far side of the hills flanking the east bank of the Neath. This rose to a height of 229 m (750 ft) by means of a steep incline and a vertically sided walled embankment. These features are a scheduled ancient Monument. At the summit there was a deep cutting through rock. There were in all six gravity inclines and one powered by a stationary steam engine. it was abandoned in 1867.

One of the photos (top right in the set of six) is by Ben Salter with our thanks.