Caerleon, an ancient village in the southern parliamentary division of Monmouthshire, England, on the right (west) bank of the Usk, 3 m. N.E. of Newport. Pop. (1901) 1411. Its claim to notice rests on its Roman and British associations. As Isca Silurum, it was one of the three great legionary fortresses of Roman Britain, established either about A.D. 50 (Tacitus, Annals, xii. 32), or perhaps, as coin-finds suggest, about A.D. 74-78 in the governorship of Julius Frontinus, and in either case intended to coerce the wild Silures. It was garrisoned by the Legio II. Augusta from its foundation till near the end of the Roman rule in Britain. Though never seriously excavated, it contains plentiful visible traces of its Roman period - part of the ramparts, the site of an amphitheatre, and many inscriptions, sculptured stones, etc., in the local museum. No civil life or municipality seems, however, to have grown up outside its walls, as at York (Eburācum). Like Chester (see Deva), it remained purely military, and the common notion that it was the seat of a Christian bishopric in the 4th century is unproved and improbable. Its later history is obscure. We do not know when the legion was finally withdrawn, nor what succeeded.

But Welsh legend has made the site very famous with tales of Arthur (revived by Tennyson in his Idylls), of Christian martyrs, Aaron and Julius, and of an archbishopric held by St Dubric and shifted to St David's in the 6th century. Most of these traditions date from Geoffrey of Monmouth (about 1130-1140), and must not be taken for history. The ruins of Caerleon attracted notice in the 12th and following centuries, and gave plain cause for legend-making. There is better, but still slender, reason for the belief that it was here, and not at Chester, that five kings of the Cymry rowed Edgar in a barge as a sign of his sovereignty (A.D. 973). The name Caerleon seems to be derived from the Latin Castra legionum, but it is not peculiar to Caerleon-on-Usk, being often used of Chester and occasionally of Leicester and one or two other places.

(F. J. H.)