The Glamorganshire Canal, backed by the principal ironmasters of Merthyr Tydfil, was built to carry iron twenty five and a half miles from Merthyr to the port of Cardiff, descending (originally) through 50 locks. It was opened on 10 February 1794 and became the most successful canal in south Wales. A southern extension giving direct access to the Bristol Channel and known as the sea pound (nprn 400534) was opened in 1798. The Aberdare Canal (nprn 85373) branched off from Abercynon and the Doctor's Canal (nprn 85391) branched from Denia to Treforest. Control of the Glamorganshire and Aberdare Canals passed to the Marquis of Bute in 1885. Merthyr to Abercynon closed 1898, Abercynon to Pontypridd closed 1915, Pontypridd to Cardiff closed 1942 and Cardiff sea pound (nprn 400534) closed 1951. Remains of the canal are now scanty, having been built over by realignments of the A470 trunk road.
B.A.Malaws, RCAHMW, 03 February 2004.