At one time boats were hauled by hand across the isthmus between the two Bays. The canal was built during the Great Famine between 1845 and 1851. It was built by hand by 200 labourers who were paid 1/- per day. In stormy weather the canal allowed relatively safe passage from Westport to Donegal for ships of up to 150 tons. Previously ships could face a delay of many days in stormy weather.