"LLANTILLIO-CROSSENNY, a parish in the upper division of the hundred of Skenfreth, county Monmouth, 7 miles N.W. of Monmouth, its post town. The village, which is small, is situated on the river Trothy. The living is a vicarage* in the diocese of Llandaff, value £270, in the patronage of the dean and chapter. The church, dedicated to St. Teilaw, is a spacious structure, in the decorated style of architecture, with lofty tower. Adjoining it is a large chapel, on the N. side of the presbytery. In the churchyard is an altar-tomb to the memory of Colonel Clifford's son." [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 established after 1851.
Llantillio-Crossenny Parish; Statistics; Area 5951 acres; Population 44 males, 34 females, total 78
Llantilio Crossenny Parish Church Attendance - morning 80 +30 scholars 1 service in English David Davies, Minister
Llanfair Chapel, Church of England Consecrated 1850 - an additional church in the Upper division of Llantilio Attendance - afternoon 50 1 service in English David Davies, Vicar of Llantilio, Crossenny
Rose Cottage Chapel, Primitive Methodist Erected 1842 Attendance - morning 45, evening 70 James Jones, Minister
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
Kain, R.J.P., Oliver, R.R., Historic Parishes of England and Wales: an Electronic Map of Boundaries before 1850 with a Gazetteer and Metadata [computer file]. Colchester, Essex: History Data Service, UK Data Archive [distributor], 17 May 2001. SN: 4348. Here is a gazetteer/finding aid plus a set of overview maps to accurately identify the position of parishes within the county.
You can see maps centred on OS grid reference SO398149 (Lat/Lon: 51.829456, -2.874976), Llandeilo Gresynni / Llantilio Crossenny which are provided by: