St Columb Major Parish
, is bounded on the north by Little Petherick and St Issey, on the east by St Wenn, Roche and St Dennis, on the south by St Enoder and Colan, and on the west by St Columb Minor, Mawgan-in-Pydar and St Ervan. This parish is named after the patron, Saint Columba.
William of Worcester wrote of an ancient castle at Carloggas, which was in ruins in the medieval period in which he lived; also of a turretted mansion, which had belonged to John Tregoos Esq., but of these no vestiges remain. About two miles south-east of St Columb town stands Castle-an-Dinas, which appears to have been from the pre-Roman Iron Age period. There are other relics from this period in the parish. The Arundells were the most influential family here; Sir John Arundell, who died in 1379, lies buried in the church.
The town of St Columb is built on an eminence, and had a number of good-quality houses. Edward III granted a market here to Sir John Arundell in 1333. A little below the town to the eastwards stood the St Columb Union Workhouse. The principal villages in the parish are: Glivian, Halloon, Lanhizey, Rosedinick, Rosevanion, Ruthvoes (or Ruthvos), Tolskedy, Tregamere, Tregaswith, Tregatilian, Trekenning, Trebadannon, Trevarron
, Trevolgas and Trugo. A number of mines were worked in the parish - both tin and manganese; there was also much good farming.