The Ulster Canal is a canal running through part of County Armagh, County Tyrone and County Fermanagh in Northern Ireland and County Monaghan in the Republic of Ireland. The Ulster Canal was built between 1825 and 1842 and was 74 km (46 mi) long with 26 locks. It ran from Charlemont on the River Blackwater to near Wattlebridge on the Finn River, south-east of Upper Lough Erne. It was an ill-considered venture, with the locks built narrower than the other Irish waterways, preventing through trade, and an inadequate water supply. It was an abject failure commercially, and contributed to the collapse of the Lagan Navigation Company, who took it over from the government but were then refused permission to abandon it when they could not afford the maintenance costs. It finally closed in 1931. Waterways Ireland started work on rebuilding the canal at its southern end in 2015.