The Borough of Islwyn was one of five local government districts

Districts of Wales

In 1974, Wales was re-divided for local government purposes into thirty-seven districts. Districts were the second tier of local government introduced by the Local Government Act 1972, being subdivisions of the eight counties introduced at the same time...

 of Gwent

Gwent (county)

Gwent is a preserved county and a former local government county in south-east Wales. It was formed on 1 April 1974, under the Local Government Act 1972, and was named after the ancient Kingdom of Gwent....

 from 1983 to 2011.
The district was formed under the Local Government Act 1972

Local Government Act 1972

The Local Government Act 1972 is an Act of Parliament in the United Kingdom that reformed local government in England and Wales on 1 April 1974....

 from part of the administrative county

Administrative county

An administrative county was an administrative division in England and Wales and Ireland used for the purposes of local government. They are now abolished, although in Northern Ireland their former areas are used as the basis for lieutenancy....

 of Monmouthshire

Monmouthshire

Monmouthshire is a county in south east Wales. The name derives from the historic county of Monmouthshire which covered a much larger area. The largest town is Abergavenny. There are many castles in Monmouthshire .-Historic county:...

, namely the urban district

Urban district

In the England, Wales and Ireland, an urban district was a type of local government district that covered an urbanised area. Urban districts had an elected Urban District Council , which shared local government responsibilities with a county council....

s of Abercarn

Abercarn

Abercarn is a small town community in Caerphilly county borough, Wales, 10 miles north-west of Newport on the A467 between Cwmcarn and Newbridge, within the historic boundaries of Monmouthshire.-History:...

, Mynyddislwyn

Mynyddislwyn

Mynyddislwyn was a civil parish and urban district in Monmouthshire, south east Wales. It was abolished in local government reorganisation in 1974.The ancient parish of Mynyddislwyn covered a large part of the lower Ebbw and Sirhowy Valleys...

 and Risca

Risca

Risca is a town of approximately 11,500 people in South Wales, within the Caerphilly County Borough and the historic boundaries of Monmouthshire. It is today part of the Newport conurbation , though it is not a Ward of Newport City Council...

, and the Bedwellty

Bedwellty

Bedwellty was a parish and urban district in Monmouthshire, South Wales, until 1974.The original ancient parish was very large, including most of the upper Ebbw and Sirhowy valleys...

 urban district less the wards of Aberbargoed

Aberbargoed

Aberbargoed is a small town in the Welsh county borough of Caerphilly, within the historic boundaries of Monmouthshire, south Wales. Aberbargoed once contained the largest ever colliery waste tip in Europe, although this has now been reclaimed and turned into a country park.- Mining :Coal mining...

, Cwmsyfiog, New Tredegar

New Tredegar

New Tredegar is a former coal mining community in the Rhymney Valley, Caerphilly county borough, Wales , within the historic boundaries of Monmouthshire....

 and Phillipstown.

The district's name (meaning "below the grove") was derived from the ancient parish of Mynyddislwyn which covered its area. This was shown in the borough's coat of arms

Coat of arms

A coat of arms is a unique heraldic design on a shield or escutcheon or on a surcoat or tabard used to cover and protect armour and to identify the wearer. Thus the term is often stated as "coat-armour", because it was anciently displayed on the front of a coat of cloth...

 which represented a mountain below a grove of oak trees. Islwyn was also the nom de plume of local poet William Thomas

William Thomas (Islwyn)

William Thomas, bardic name Islwyn , was a Welsh language poet, born near Ynysddu, then in the old county of Monmouthshire, south-east Wales.- Early life :...

 (1832-1878).

The borough was abolished in 1996, when its area became part of Caerphilly County Borough.

Islwyn continues as a Westminster constituency

Islwyn (UK Parliament constituency)

Islwyn is a constituency represented in the House of Commons of the Parliament of the United Kingdom.This area, historically known for coal-mining, is a safe Labour Party seat latterly held by the former Leader of the Opposition Neil Kinnock...

 and a Welsh Assembly constituency

Islwyn (National Assembly for Wales constituency)

Islwyn is a constituency of the National Assembly for Wales. It elects one Assembly Member by the first past the post method of election. Also, however, it is one of eight constituencies in the South Wales East electoral region, which elects four additional members, in addition to eight...

.