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 mile in Ireland.

The historic clan territories of the county included Uí Drona (O'Ryan), Fothairt Feadh (O'Nolan), Uí Ceinnselaig (Kinsella), Dál Coirpri Cliach (Kerwick), Uí Bairrche Magh dá chonn (Kearney), Uí Felmeda Tuaidh (O'Garvey) and Uí Bairrch Maige hAilbe (O'Gorman).

With the exception of a short-lived Norse–Gael settlement near St. Mullin's in the 9th century, the area remained under the control of the Kingdom of Leinster until the 13th century.

Following the Norman conquest, the "Borough of Carlow" was founded in July 1210, and formed part of the Norman palatine county of Leinster. This was later divided, and the independent Liberty of Carlow was established in 1247. At that time the county was over three times larger than it is today,

The alliance between the…