The nineteenth century brought a transport revolution to the town with the arrival of the Royal Canal in 1806 and the railway in 1848. Mullingar was also an important coach stop.
The rise of a Roman Catholic middle class and an active Clergy led to the building of a Cathedral in 1836 and the founding of schools by the Presentation and Loreto Sisters and the Christian Brothers. There was also a Church of Ireland National School.
Nineteenth century Mullingar was an important military centre and many British army regiments were stationed in the town. Many of the soldiers married local women and settled in town. The army also supplied a source of employment for locals and men from Mullingar served all over the British Empire.
In 1858, Lord Greville purchased the town and his family remained Landlords until the 1920s. In 1868, Lord Greville leased a Right of Way to the War Minister for 10,000,000 years – the longest lease in the world.
As well as a Cathedral, a military barracks, a railway station and the canal, Mullingar in the 1800s also had an infirmary, a workhouse, a jail, a courthouse, a market house, a post office and a police barracks. There was also a racecourse. The town was lit by gas from 1859 and a telegraph office opened in 1853. Mullingar Town Commissioners were founded in 1856. A District Dispensary opened in the 1850s, as did St. Loman’s Mental Hospital. Sports played in the town included Rugby, Cricket and Gaelic games. Confraternities, Temperance Clubs, Freemasonry and the Foresters provided a social life and welfare.
Poverty was also a feature of 19th century Mullingar. There was much poor housing and periodic outbreaks of Cholera and other disease. A lack of sufficient employment and the ravages of the Great Famine led to an upsurge of emigration to Britain, America, Australia, Canada and Argentina. Changing agricultural practices, recession and unjust land laws led to many evictions and much violence in parts of the rural hinterland during the 1860s and 1870s.