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|- 1911||7,275 acres (29.4 km2)|
|- 1961||7,353 acres (29.8 km2)|
|- Succeeded by||Islwyn, Rhymney Valley|
The original ancient parish was very large, including most of the upper Ebbw and Sirhowy valleys. A number of coal mining communities grew up in the parish, and in the 19th century these became separate local government units.
On 19 June 1874, Ebbw Vale, Rhymney and Tredegar local boards of health and local government districts were formed, each including parts of the civil parish. The remainder of Bedwellty itself became a local government district on 29 June 1891. In 1894 the local boards were replaced by urban districts. The areas included in Bedwellty, Ebbw Vale, Rhymney and Tredegar urban districts became separate civil parishes.
In 1926 Bedwellty and Mynyddislwyn urban districts formed the West Monmouthshire Omnibus Board to ensure local control of bus services. In 1935 a County Review Order altered the boundaries between Bedwellty and Mynyddislwyn.
The urban district was abolished by the Local Government Act 1972 in 1974. Its area was split: the wards of Aberbargoed, Cwmsyfiog, New Tredegar and Phillipstown passed to the Rhymney Valley district of Mid Glamorgan, and the remainder was included in the Islwyn borough of Gwent.
Further local government reorganisation in 1996 has led to the area of the former urban district being included in the county borough of Caerphilly. It now corresponds to the communities of Aberbargoed, Argoed, Bargoed, Blackwood, Cefn Fforest, New Tredegar, and part of the community of Darran Valley.
The parliamentary constituency of Bedwellty was created in 1918 covering a much larger area. It continued to exist until 1983, when it was replaced by the constituency of Islwyn. The member of parliament for the Bedwellty and Islwyn constituencies from 1970 to 1995 was Neil Kinnock, who took the title Baron Kinnock, of Bedwellty in the County of Gwent in 2005.