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A map of Carlow
Historical populationYearPop.±%18136,146—    18218,035+30.7%18319,114+13.4%184110,409+14.2%18518,690−16.5%18618,344−4.0%18717,842−6.0%18817,185−8.4%18916,619−7.9%19016,513−1.6%19116,619+1.6%19267,163+8.2%19367,649+6.8%19467,466−2.4%19517,667+2.7%19568,445+10.1%19618,920+5.6%19669,765+9.5%197110,399+6.5%198113,164+26.6%198613,816+5.0%199114,027+1.5%199614,979+6.8%200218,487+23.4%200620,724+12.1%201123,030+11.1%201624,272+5.4%202227,351+12.7%
Evidence shows that human occupation in the Carlow county area extends back thousands of years. The most notable and dramatic prehistoric site is the Browneshill Dolmen – a megalithic portal tomb just outside Carlow town.
Now part of the diocese of Kildare and Leighlin, several Early Christian settlements are still in evidence today around the county. St Mullin's monastery is believed to have been established around the 7th century, the ruins of which are still in evidence today. Old Leighlin was the site of one of the largest monastic settlements in Ireland and the location for a church synod in 630 AD which determined the date of Easter. St Comhgall built a monastery in the Carlow area in the 6th century, an old church building and burial ground survive today at Castle Hill known as Mary's Abbey. Carlow was an Irish stronghold for agriculture in the early 1800s which earned the county the nickname of the scallion eaters. Famine later wiped out half of the population.
Carlow Castle was constructed by William Marshal, Earl of Striguil and Lord of Leinster, c. 1207 – c. 1213, to guard the vital river crossing. It was also to serve as the capital of the Lordship of Ireland from 1361 until 1374. This imposing structure survived largely intact until 1814 when it was mostly destroyed in an attempt to turn the building into a lunatic asylum. The present remains now are the West Wall with two of its cylindrical towers.
Carlow was incorporated as a borough in 1296 by Edward I. The parliamentary borough returned two MPs to the Irish House of Commons until 1801 and its successor constituency returned one MP to the United Kingdom House of Commons from 1801 to 1885.
The bridge over the River Barrow, Graiguecullen Bridge, is agreed to date to 1569. The original structure was largely replaced and widened in 1815 when it was named Wellington Bridge in celebration of the defeat of Napoleon's army by the Duke of Wellington at the Battle of Waterloo in June of that year. The bridge was built across a small island in the river and a 19th-century house was constructed on the bridge – this was for a time occupied by the Poor Clares, an enclosed religious order who still have a convent in Graiguecullen.
Another convent belonging to the Presentation Order of nuns now houses the County Library and the Carlow County Museum. The cathedral, designed by Thomas Cobden, was the first Catholic cathedral to be built in Ireland after Catholic emancipation in 1829. Its construction cost £9,000 and was completed in 1833.
Saint Patrick's College, located beside the cathedral, dates from 1793. The college was established in 1782 to teach the humanities to both lay students and those studying for the priesthood. The Carlow Courthouse was constructed in the 19th century. There are still many old estates and houses in the surrounding areas, among them Ducketts Grove and Dunleckney Manor. St Mullin's today houses a heritage centre.
In 1703, the Irish House of Commons appointed a committee to bring in a bill to make the River Barrow navigable; by 1800 the River Barrow Track was completed between St. Mullin's and Athy, establishing a link to the Grand Canal which runs between Dublin and the Shannon.
Distant view of Carlow to the north, Dublin Penny Journal, 1834
By 1845, 88,000 tons of goods were being transported on the River Barrow Navigation. Carlow was also one of the earliest towns to be connected by train.
The Great Southern and Western Railway had opened its mainline as far as Carlow in 1846, and this was extended further to Cork in 1849. The chief engineer, William Dargan, originally hailed from Killeshin, just outside Carlow. At the peak of rail transport in Ireland, Carlow county was also served by a line to Tullow.
Dublin Street, Carlow circa 1900
Public supply of electricity in Carlow was first provided from Milford Mills, approximately 8 km south of Carlow, in 1891. Milford Mills still generates electricity feeding into the national grid. Following independence in the early 1920s, the new government of the Irish Free State decided to establish a sugar-processing plant in Leinster. Carlow was chosen as the location due to its transport links and large agricultural hinterland, favourable for growing sugar beet.
The town is recalled in the famous Irish folk song,"Follow Me Up to Carlow", written in the 19th century about the Battle of Glenmalure, part of the Desmond Rebellions of the late 16th century. In 1650, during the Cromwellian conquest of Ireland, Carlow was besieged and taken by English Parliamentarian forces, hastening the end of the Siege of Waterford and the capitulation of that city.
During the 1798 rebellion, Carlow was the scene of a massacre of 600 rebels and civilians following an unsuccessful attack on the town by the United Irishmen, known as the Battle of Carlow. The Liberty Tree sculpture in Carlow, designed by John Behan, commemorates the events of 1798. The rebels slain in Carlow town are buried in the 'Croppies Grave', in '98 Street, Graiguecullen.
On 1 June 2025, Evan Fitzgerald fired shots in the Tesco at Fairgreen Shopping Centre in the town, which resulted in his death and the injury to a young girl while fleeing the shots. The sounds of shots were captured on a nearby barber's CCTV. Armed local police responded as well as bomb disposal units. This event is notable as it is one of the first known active shooter-style events in Ireland
