The Great Irish Famine of the mid-19th century had caused a huge wave of emigration, and the population of Ireland was reduced from about 8 million in the 1830s to around 4 million a century later. The worst hit were the rural population of the west, precisely the market of the MGWR. There was a brief period of boom in the 1870s as the flow of people from the west peaked, but as the people left, traffic in the other direction reduced markedly. As emigration gradually came to a halt, so did the canal system.
The MGWR was never very interested in the canal business and in 1877 they were given permission by the government to close 150 yards (140 m) of the branch line and to fill in the harbour, to construct a new forecourt for the station. That removed the need for a movable pontoon bridge, and a new approach road, Western Way, was built by way of Foster Aqueduct. The harbour was no longer needed due to the construction of one larger and better situated at Spencer Dock, and was filled in to become the forecourt of Broadstone Station.
The small reservoir had been made almost redundant by the construction of a new reservoir at Vartry in 1868, and served only the Jameson Whiskey distilleries at Smithfield, until they left the city in the 1970s.
By the 1920s average annual tonnage on the Royal Canal
had reduced to 10,000 tons. In 1924 the MGWR amalgamated with its rival, the Great Southern and Western Railway, to enable rationalisation and survival, and in 1927 the bridged section under Foster aqueduct was filled in, and the canal and railway were permanently disconnected.
By the 1930s the railway was failing too and the last train arrived from Westport in 1937. In 1944 the Canal and Railway both passed into the ownership of the state transport company Córas Iompair Éireann (CIÉ), which transferred all its steam locomotives there in 1954. However, when steam locomotion ended in 1961, Broadstone was closed. Foster Aqueduct was removed in 1951 to facilitate road widening.
Today the historic building is used as offices by Bus Éireann and the rest of the site is used a parking and servicing area for buses, with the main building mostly obscured by public housing and light industrial buildings.
After the closure of the railway came the hardships of the war, rationing, and a prolonged recession. Unemployment and deprivation hit the inhabitants of Dublin's north inner city hard, and the area around Dominick Street, Grangegorman and Broadstone was one of the worst affected by drug abuse, especially heroin. The park at Royal Canal Bank and the disused reservoir at Blessington Street were magnets for delinquents, as was the dereliction around Paradise Place.
The Irish Youth Hostelling association, An Óige, took over the old convent building on Mountjoy Street and this now serves as both the headquarters of the organisation and its main international hostel in Dublin.