It is today believed that the first part of the name derives from the Old Irish word cethrae ("animals, cattle, herds, flocks"), which is related to ceathar ("four") and therefore signified "four-legged".

[9] Some of the oldest deciduous trees in the county are found in the yew grove at the Huntington Gardens, which were planted by the Esmonde family over 500 years ago.

123 acre mixed forest of beech, oak, Scots pine, silver fir, larch and sycamore; the Altamont Gardens and the Barrow Way.

Met Éireann records climate data for Carlow from their station at Oak Park, situated at 61 m (200 ft) above sea level.

While Carlow is often marketed as being part of the Sunny Southeast alongside Wexford and Waterford, due to its inland location it does not typically benefit from the elevated sunshine hours observed in the coastal areas of those counties.

[14] The north of the county is generally flat, while central and southern Carlow are characterised by an undulating to rolling topography which becomes progressively hillier towards the south and east.

[20] As was the case in much of Ireland, Fianna Fáil and Fine Gael emerged as the two dominant parties in the 2024 local elections, holding 11 of the 18 seats between them.

[30] The area of present-day Carlow has been inhabited for thousands of years, and the county has perhaps the highest concentration of megalithic monuments per square kilometre in Ireland.

During this period, Carlow was part of the patrimony of the Anglo-Norman Butler dynasty; however Art MacMurrough-Kavanagh, the ascendant King of Leinster, controlled more than half of the liberty.

In the late 15th-century, James Butler, the 9th Earl of Ormond, purchased land within the county to give to his heirs, rather than enter into conflict with the dynasty.

The informal alliance between the Kingdom of Leinster and the Anglo-Normans remained the status quo for decades, as it kept the peace and made both sides immensely wealthy.

In a bid to halt the decline of English authority in the region, the crown made Carlow the capital of the Lordship of Ireland from 1361 until 1374, just 13 km (8.1 mi) north of MacMurrough-Kavanagh's permanent residence at Leighlin.

[35] Large areas on the northern and eastern fringes of the Liberty of Carlow gradually fell completely to the O'Moores, O'Byrnes and other chiefdoms.

Carlow retained its Irish Sea border, though control of this land became disputed with the ruling chiefs of the area who were petitioning for their own shire.

However, in the wake of the French Revolution, local members of the Orange Order organised into a Yeomanry Cavalry Corps which conducted nightly raids on Catholic and Dissenter homes, often burning them to the ground, in search of weapons and revolutionary literature.

[38] As feelings of persecution and religious division grew amongst the overwhelmingly Catholic populace, local United Irish leader Laurence Griffin lamented "the people of Carlow think of all Protestants as Orangemen".

Catholics and non-Anglican Protestants could not vote to effect change, so they eventually joined forces with radical liberal Anglicans to overthrow the Parliament.

[41] Plagued by poor supply-lines and hindered by a heavy Royal Irish Constabulary (RIC) presence, the Carlow Brigade was one of the least active of the war and mostly specialised in delaying tactics such as blocking roads, destroying bridges and intercepting mail.

The brigade carried out a botched ambush near Ballymurphy in April 1921, with the loss of 12 members (4 killed and 8 captured) and vital munitions, after which no further active engagements with either the RIC or British Army were attempted.

[43] Carlow saw relatively little action during the Civil War, as the Free State Army deployed hundreds of soldiers to the former RIC strongholds within the county, effectively strangling the Irregulars.

The Brownshill Dolmen, situated on the Hacketstown Road (R726), has a capstone which weighs an estimated 100 metric tons, and is reputed to be the heaviest in Europe.

A total of 57 archaeological sites were identified along the proposed route and yielded a variety of relics, including flint arrowheads and bone scrapers, pottery, hammers and axeheads made of granite and an Iron Age glass bead.

[63] Although stone castles were generally of far superior quality, wooden structures were still favoured by the more mobile Irish kingdoms, as they could be easily constructed and abandoned when necessary.

Although the term was never applied at the time, historian Jimmy O'Toole refers to Carlow as "the most gentrified county in Ireland" due to the concentration of aristocratic families and their grand estates within its borders.

[79] The Blackstairs Mountains are a designated Special Areas of Conservation (SAC) and contain a diverse range of habitats which are protected under Irish and European law.

[125] This latter symbol makes Carlow's coat of arms unique in the Republic of Ireland, where British monarchical emblems are not typically present on local or national government seals.

The town's coat of arms displays a green and yellow flag with the Butler red lion in the centre, flying over Carlow Castle.

Out of 112 entries, a song entitled "The Red, Yellow and Green" by country singer Derek Ryan was chosen as the winner by a live audience and panel of judges.

[131][132] The VISUAL Centre is located on the Old Dublin Road in Carlow town and hosts a contemporary art museum as well as the George Bernard Shaw Theatre.

The Festival of Writing and Ideas is held each year on the grounds of Borris House and features live discussions with novelists, poets and journalists.