The canal was closed to navigation in 1949, however its line remains intact and the towpath is currently part of the National Cycle Network and the Ulster Way long distance footpath.

To enhance the capacity of the navigation, the Newry Ship Canal was constructed, running a further 3½ miles south from Albert Basin to the deeper waters of Carlingford Lough.

By 1800, the Newry Canal was in a poor condition, and another £57,000 of public money was spent refurbishing it over the following ten years.

Despite the order, no work was carried out, nor was it when Francis Nevil, a tax collector for the government, made a similar survey and proposal in 1703.

In order to address the situation, the Irish Parliament in 1717 offered a reward of £1,000 to the first person to produce 500 tons of native coal in Dublin[2] and the Commissioners of Inland Navigation for Ireland were set up in 1729, consisting of three high officials from the government, four bishops, and eighty responsible persons, who would oversee all matters concerned with inland waterways.

[3] With the hope that a good transport route from the Tyrone coalfields to Dublin could result in the city becoming self-sufficient in coal, rather than having to rely on imports from Great Britain, which were often intermittent, the canal was approved by the commissioners.

Although Pearce was officially running the scheme, he was busy constructing the new Parliament House at the time, and gave the task to one of his architectural assistants, Richard Cassels.

[6] He was replaced by Thomas Steers, who employed a local man called William Gilbert to oversee the work, which was completed by 1741.

[7] Legal disputes delayed the official opening until 1742, and a barge loaded with coal from the Tyrone coalfields reached Dublin on 28 March 1742, although the first part or the journey had involved carriage of the coal overland to Lough Neagh, as the Tyrone Navigation, begun in 1732, was far from complete.

[6] The Newry Canal has 14 locks, nine of them to the south of the summit, which is 23.8 metres (78 ft) above the level of Carlingford Lough.

They were 3.7 to 4.0 metres (12 to 13 ft) deep[8] and each lock was faced with stone from the Benburb quarries early in the 1800s after the original brick sides began to crumble.

Despite the manager, Acheson Johnston, having to report to Parliament in 1750 that there were defective locks, water shortage problems and issues with the width of the summit section, the merchants of Newry were keen to develop the town as a port, and obtained a government grant to build a ship canal to the town.

Omer ignored the previously planned route, and created a 3.2-kilometre (2 mi) ship canal which could accommodate boats of up to 120 tonnes.

Henry Walker, an engineer, was asked to put it back into good order, but was imprisoned and then deported to America for acting fraudulently.

John Brownrigg then produced a detailed report of its condition, in which he suggested it would be cheaper to build a new canal than repair the existing one, but his advice was ignored.

As the refurbishment involved the rebuilding of many bridges and locks, widening and deepening the summit level, there were long periods where the canal was effectively closed.

The water supply was improved, and the ship lock was restored, but inevitably, closures resulted in traffic transferring to road transport, and it proved difficult to attract it back to the canal, once the work was completed in 1811.

All suggested that a larger sea lock was required in deeper water, and that the ship canal needed to be enlarged.

The Directors General objected, as they had not been consulted, and felt that it was wrong to transfer an undertaking that had been built using public money to a private company.

The owning company was still saddled with debts from the engineering projects carried out since 1829, and coal traffic from the Tyrone collieries had all but ceased.

[14] In 1884, the company carried out its last major engineering project, when the upper reaches of Carlingford Lough and the lower Newry River were made deeper, and the navigable channel widened to 37 metres (120 ft).

It is now part of the Ulster Way long-distance footpath, and has been incorporated into the National Cycle Network's[25] Route 9 which will eventually link Belfast with Dublin.