During the First World War, traffic dropped by half, but after hostilities ended, the government returned the canal to private ownership, some £20,000 was spent on repairs, and traffic flourished.
In the 1920s, traffic from Belfast to Lisburn averaged 307,033 tons of coal and 19,126 tons of other goods.
Traffic above Lisburn was much lower, but some coal continued to reach the Ulster Canal until it was closed in 1931.
There were large cargoes of sand and gravel travelling in the opposite direction, originating on the east Tyrone shores of Lough Neagh, and used for building projects in Belfast.
The years immediately before the Second World War saw a collapse in commercial canal traffic.
Downstream traffic dropped from 29,000 tons to 600 tons between 1931 and 1941, while upstream traffic dropped from 87,000 tons to 28,000 tons.
The canals were thought to be too slow, compared to roads and railways.

With their funds exhausted, the company considered closure of their canal and the Coalisland Canal.
However, there was a clause in the Act of Parliament from 1843 which stated that if the canals became unnavigable, the Lagan Navigation Company would automatically cease to exist.
Rather than create an awkward political situation, where the Ministry of Commerce inherited canals that were already defunct, the government made payments to the company to cover operating losses and some repairs to the infrastructure.
Between 1938 and 1952, these payments amounted to £130,000.
There had been no traffic above Lisburn since 1947, and the Ministry of Commerce announced that the canals would close in the spring of 1954.
The Inland Navigation Act (NI) was passed in April 1954, and the Coalisland Canal, the Upper Bann Navigation and the Lagan Canal above Lisburn were closed.
Below Lisburn, the canal remained open for another four years, but was closed on 1 July 1958.
In 1965, some 7.7 miles (12.4 km) of the central section, between Moira and Sprucefield, were destroyed by the building of the M1 motorway along its route.
During the First World War, traffic dropped by half, but after hostilities ended, the government returned the canal to private ownership, some £20,000 was spent on repairs, and traffic flourished. In the 1920s, traffic from Belfast to Lisburn averaged 307,033 tons of coal and 19,126 tons of other goods. Traffic above Lisburn was much lower, but some coal continued to reach the Ulster Canal until it was closed in 1931. There were large cargoes of sand and gravel travelling in the opposite direction, originating on the east Tyrone shores of Lough Neagh, and used for building projects in Belfast. The years immediately before the Second World War saw a collapse in commercial canal traffic. Downstream traffic dropped from 29,000 tons to 600 tons between 1931 and 1941, while upstream traffic dropped from 87,000 tons to 28,000 tons. The canals were thought to be too slow, compared to roads and railways.
With their funds exhausted, the company considered closure of their canal and the Coalisland Canal. However, there was a clause in the Act of Parliament from 1843 which stated that if the canals became unnavigable, the Lagan Navigation Company would automatically cease to exist. Rather than create an awkward political situation, where the Ministry of Commerce inherited canals that were already defunct, the government made payments to the company to cover operating losses and some repairs to the infrastructure. Between 1938 and 1952, these payments amounted to £130,000. There had been no traffic above Lisburn since 1947, and the Ministry of Commerce announced that the canals would close in the spring of 1954. The Inland Navigation Act (NI) was passed in April 1954, and the Coalisland Canal, the Upper Bann Navigation and the Lagan Canal above Lisburn were closed. Below Lisburn, the canal remained open for another four years, but was closed on 1 July 1958. In 1965, some 7.7 miles (12.4 km) of the central section, between Moira and Sprucefield, were destroyed by the building of the M1 motorway along its route.
Lagan Canal