In 1789, Dublin Corporation commissioned the Royal Canal and a harbour built on Constitution Hill, connected to the main canal at Phibsboro by a spur. In many ways the history of Broadstone is the history of this canal. Though the branch line was completed by 1796, it was ten more years before the harbour was opened; construction continued for some years afterwards. The harbour's location was chosen for its proximity to the markets and the law courts.
By 1807 a regular passage boat service was operating to Mullingar. In subsequent years the area was a hive of industry, with many hotels and inns and the trade boats using the wharfage and stores at the harbour. The canal was linked eventually with the River Shannon in 1817, after many financial difficulties, and the majority of the main route still exists. In 1810 a reservoir, the Blessington Basin, was dug from the spur to supply water to the locality.
Average annual tonnage on the canal in the 1830s was 80,000 tons and 40,000 passengers.