In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Mynyddislwyn like this:
MYNYDDYSLWYN, a village, a parish, and a sub-district, in Newport district, Monmouth. The village stands 1½ mile E of the river Sirhowy, 2½ E by S of Tredegar-Junction r. station, and 9½ N W of Newport. The parish comprises the hamlets of Clawrplwyf, Mynydd-maen, and Penmaen; and contains the town of Abercarn, which has a post-office under Newport, Monmouth. Acres, 15, 938. Real property, £29, 971; of which £12, 970 are in mines, £60 in quarries, £220 in iron-works, and £3, 446 in railway s. ...
Pop. in 1851, 5, 994; in 1861, 6, 877. Houses, 1, 393. The property is sub-divided. The surface is hilly and boldly undulating; and descends to the rivers Sirhowy and Ebbw. Chemical works, iron and tin-plate works, and extensive collieries are at or near Abercarn. A large tumulus, supposed to have been a beacon or signal station, is near thechurch. The parish is a meet for the Tyisha harriers. The living is a p. curacy in the diocese of Llandaff. Value, £160.* Patron, the Bishop of Llandaff. The church is large and good; and has a tower, rebuilt in 1821. The p. curacy of Penmaen is a separate benefice. There are chapels for Independents, Baptists, Calvinistic Methodists, Wesleyans, and Roman Catholics. Ruins ofan ancient chapel of ease are in the vicinity of Abercarn.The sub-district contains also Machen parish, and twohamlets of Bedwas. Acres, 25, 311. Pop., 10, 596. Houses, 2, 147.
A Vision of Britain through Time includes a large library of local statistics for administrative units. For the best overall sense of how the area containing Mynyddislwyn has changed, please see our redistricted information for the modern district of Caerphilly. More detailed statistical data are available under Units and statistics, which includes both administrative units covering Mynyddislwyn and units named after it.
GB Historical GIS / University of Portsmouth, History of Mynyddislwyn, in Caerphilly and Monmouthshire | Map and description, A Vision of Britain through Time.
Date accessed: 28th July 2015
Click here for more detailed advice on finding places within A Vision of Britain through Time, and maybe some references to other places called "Mynyddislwyn".