"TREDUNNOCK, a parish in the upper division of Usk hundred, county Monmouth, 3½ miles S. of Usk, its post town, and 4 from Caerleon, on the river Usk. The living is a rectory in the diocese of Llandaff, value £208. The church, dedicated to St. Andrew, contains an effigy in slate of a Roman soldier of the second legion, which was discovered near the foundation of the building. The parochial charities produce about £4 per annum."
[Description(s) from The National Gazetteer of Great Britain and Ireland (1868)
Church and chapel data from The Religious census of 1851 : A Calendar of the returns relating to Wales, Vol 1, South Wales. Ed. by I.G Jones, & D. Williams. UWP, Cardiff, 1976. The names given towards the end of each entry are those of the informants. Check with Gwent RO to see what extant records are held, and possible names of chapels/churches built after 1851.
Tredunnock Parish; Statistics; Area 1393 acres; Population 88 males, 69 females, total 157
Tredunnock Parish Church Attendance - morning 18, afternoon 25 (alternate?) 1 service in English Informant; Edward Williams
Family Search have an interactive map called "England and Wales Jurisdictions 1851" showing parish (and other) boundaries with optional background maps such as Ordnance Survey. There is also a Search facility, do read the guidance notes to get maximum benefit from this useful resource. See here for further background information to assist in the interpretation of this data
You can see maps centred on OS grid reference ST379948 (Lat/Lon: 51.648549, -2.898949), Tredynog / Tredunnock which are provided by: