"LLANSOY, a parish in the upper division of the hundred of Ragland, county Monmouth, 7 miles N.W. of Chepstow. Usk is its post town. It is a small agricultural place. The living is a rectory* in the diocese of Llandaff, value £170. The charities amount-to about £14 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 established after 1851.
Llansoy Parish; Statistics; Area 1410 acres; Population 86 males, 80 females, total 166
Llansoy Parish Church Attendance - morning 26 + 11 scholars, afternoon 58 + 13 scholars 1 service in English "There is no other place of worship in the parish" Richard Macdonnell Evanson, Rector
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 SO442024 (Lat/Lon: 51.717537, -2.809121), Llan-soe / Llansoy which are provided by: