In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Trelleck like this:
TRELLECK, a township and a sub-district in Monmouth district, and a parish partly also in Chepstow district, Monmouthshire. The township lies 4½ miles S by W of Monmouth r. station; takes its name from a group of monoliths, locally associated with Harold; and has a post-office under Chepstow. ...
Real property, £979. Pop., 128. Houses, 29. The parts of the parish in Monmouth district comprise 5,287 acres. Real property, £3,315. Pop., 991. Houses, 209. The property is divided among a few. A tumulus, 450 feet in circuit, is near the group of monoliths; and is said to have been the site of a castle of the Earls of Clare. The part of the parish in Chepstow district is Trelleck-Grange chapelry, Acres of the entire parish, 7,061. Pop., 1,128. Houses, 231. The living is a vicarage, united with Penalth, in the diocese of Llandaff. Value, £430.* Patron, the Bishop of L. The church is good. The p. curacy of Trelleck-Grange is a separate benefice. There are an endowed school with £43 a year, and charities £24.The sub-district includes 10 other parishes, and comprises 26,444 acres. Pop., 4,797. Houses, 1,041.
GB Historical GIS / University of Portsmouth, History of Trelleck in Monmouthshire | Map and description, A Vision of Britain through Time.
Date accessed: 27th April 2017
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