The canal was authorised by an Act of Parliament passed on 6 June 1791, which created "The Company and Proprietors of the Neath Canal Navigation", who had powers to raise £25,000 by the issue of shares, and an additional £10,000 if necessary. As well as building the canal, the Canal Company could build inclined planes, railways or rollers if required, and could optionally use the bed of the River Neath. The canal was to run from Glynneath (called Abernant at the time), which was not as far up the valley as Pontneddfechan, to Melincryddan Pill at Neath, where it would join the river. Thomas Dadford was employed as Engineer, and construction started from Neath, northwards towards Glynneath. The canal had reached the River Neath at Ynysbwllog by 1792, when Dadford resigned to take up work on the Monmouthshire Canal. He was replaced by Thomas Sheasby, who failed to complete the canal by the November 1793 deadline given to him, and was arrested in 1794 for irregularities in the accounts of the Glamorganshire Canal. The canal company completed the building work by 1795, using direct labour, although the lock into the river was never built. Rebuilding of locks and other improvements continued to be made for several years afterwards.