For most of its currently (2018) navigable 35-mile (56 km) length[1] it runs through the Brecon Beacons National Park, and its present rural character and tranquillity belies its original purpose as an industrial corridor for coal and iron, which were brought to the canal by a network of tramways and/or railroads, many of which were built and owned by the canal company.

3. c. 102), passed on 11 June 1792, which created the Company of Proprietors of the Monmouthshire Canal Navigation and empowered it to raise £120,000 by the issuing of shares, and a further £60,000 if required.

The act stated that the canal would run from Pontnewynydd to the River Usk near Newport, and would include a branch from Crindau to Crumlin Bridge.

The company also had powers to construct railways from the canal to any coal mines, ironworks or limestone quarries which were within eight miles (13 km) of it.

[2] The main line, which opened in February 1796, was 12.5 miles (20.1 km) long, and ran from Newport to Pontnewynydd, via Pontymoile, rising by 447 feet (136 m) through 42 locks.

[2] Initially work concentrated on the railways, with John Dadford overseeing the construction of lines from the collieries at Gellifelen to Llangrwyney Forge, and on to the Abergavenny to Brecon turnpike road.

[3] However costs, as usual, were higher than expected and, in 1799 Dadford stated that further money was needed to complete the section from Clydach to Brecon.

Help came from Richard Crawshay, the Merthyr Tydfil ironmaster and a major force on the Glamorganshire Canal, who provided a loan of £30,000.

[5] Two miles (3.2 km) below Brecon, the canal crosses the River Usk on an aqueduct at Brynich, and a final lock brings the total rise to 68 ft (21 m).

[3] Following Dadford's demise, Benjamin Outram was consulted on a number of matters, and recommended that the railways should be converted from edge rails to tram plates.

The Beaufort Ironworks was originally connected to Crumlin Bridge by the Ebbw Vale tramway, but the incentives for through trade which the Monmouthshire Canal Company had offered to the Brecknock and Abergavenny Company meant that carriage was cheaper if the goods originated on the northern canal, and so a second tramway was constructed along the heads of the valleys to Gilwern.

The bridge was abandoned in 1853, to eliminate the sharp curves at either end, when part of the line was converted to standard gauge, and was demolished in 1905.

[13] The Hay Railway operated through rural areas on the borders of England and Wales and was built to transport goods and freight.

[19] Restoration of the old Monmouthshire Canal began in 1994, when Torfaen Borough Council raised Crown Bridge in Sebastopol, to give sufficient height for navigation again.

[15] At the Brecon end, the canal terminates at the Theatre Basin, as a result of a project to rebuild the Brecknock Boat Company wharf, which was abandoned and infilled in 1881.

The old wharf buildings have been re-used by the Brecon Theatre, and access is provided by a new canal bridge, named after the engineer Thomas Dadford.

It will also be used to train people in the skills needed to restore historic canals, and to enable lock gates to be made locally using traditional working methods.

[26] The Taff Trail cycle route follows the canal for a few miles from Brecon, but the path after that is not suitable for cyclists with road bikes.

On 16 October 2007 a serious breach occurred when part of the canal bank near Gilwern collapsed, causing a number of houses to be evacuated.

[27] Eight people were rescued by local fire and emergency services, and the A4077 road between Crickhowell and Gilwern was closed for a period which was expected to be several weeks.

Two families were provided with temporary accommodation, and twenty-three hire boats were also affected with cranes being brought in to help them back to their bases.

[28] Contractors Noel Fitzpatrick working for British Waterways managed to reopen the road within a week of the breach occurring.

[30] Water levels on this section were reduced significantly, but engineers were then faced with the task of moving upwards of 100,000 fish before it could be drained fully.

[31] At a meeting at Crickhowell on 20 December 2007, British Waterways announced the preliminary results of the investigations: there were over 90 leaks on the section from Talybont to Gilwern, with less leakage on the stretch from Llanover to Goytre Wharf.

A press release in February 2008 announced that the total cost of restoration was likely to be around £15 million, with major investment required in the 2008/9 financial year, to repair the breach and to deal with other areas identified as being of top priority.

Their actions earned British Waterways the praise of Rhodri Glyn Thomas of the Welsh Assembly, who applauded their "courageous decision" to manage the breach in the way that they had.

The partnership submitted a bid to the Big Lottery Living Landmarks Fund for £25 million, this being 75 percent of the estimated cost of restoring the main line from Barrack Hill to Cwmbran, including the construction of a new aqueduct to take the canal over Greenforge Way, and of restoring the Crumlin Branch from Malpas Junction to the bottom of the Cefn flight of Fourteen Locks, including improvements to its water supply.

The bid reached the development stage, and the partnership successfully obtained a grant of £250,000 to enable them to undertake a full cost and engineering study for the proposed community based regeneration of the waterway.

The Canals Trust and Newport City Council made a joint presentation to the Heritage Lottery Fund for £700,000 to restore the next four locks of the flight, and this was granted on 23 March 2007.

The boats were able to cruise from Barrack Hill to Pentre Lane in Torfaen Borough for the first time in 84 years, using restored locks at Malpas, Ty Fynnon, and Tamplin.