Caus is today little more than a farm next to the remains of a Norman castle. It is situated in the foothills south of the Long Mountain, a hill spanning the England-Wales border and commanding a valley route between Shrewsbury and Montgomery. The place-name does not appear in Domesday. Eyton argued for it having been recorded under the name of Alreton, a manorial name not subsequently documented, held by someone just named Roger and whom Eyton believed to be Roger Fitz-Corbet; but current opinion has it simply as one of a number of farmsteads too insignificant to name within the manor of Worthen, although Caus is later distinguished from Worthen as a manor in its own right. A ridge-top motte-and-bailey castle had been put up by the Corbet family before 1140, perhaps by Roger Fitz-Corbet himself around the turn of the century, and their barony (comprising several manors) was named for the family's native Pays de Caux in Normandy. Roger's younger brother Robert held the nearby manor of Longden. Roger II Corbet, grandson of the original Roger, rebuilt the castle in stone from 1198. The male line of the Corbet family had died out by 1347 and the barony passed to the Stafford family, which did not keep the castle in repair.
Settlement grew up on the north side of Caus Castle, protected by an earthwork, which may have been an Iron Age hill-fort, incorporated as part of the outer defences of the Corbets' castle. This settlement likely obtained urban status around the time a Wednesday market was granted to Roger's great-grandson, Robert Corbet, in 1200, just a few years after he emerged from his minority; his main aim being presumably to assure the garrison supplies and services. It may have been in the context of founding the town that Robert granted his tenants exemption from toll in his markets – something known from a jury's assertion of the fact in 1246. Thomas Corbet, son of Robert, obtained grant of a July fair in 1248, and later that year was appointed sheriff of Shropshire; he also obtained licences for a market and fair at his Shropshire manors of Shelve (1261) and Worthen (1270). At the time of his death (1273) there were 28 burgages in Caus, which had increased to 34 by 1300.
The vulnerability of a location within the Welsh frontier zone was counter-balanced by Caus' proximity to the important trade route into Wales, and its location beside an agriculturally productive river valley. The town prospered initially: 28 burgages mentioned in 1274 had increased to 58 by 1349, and a defensive wall had been built atop the ancient rampart. But the inconvenience of access and lack of expandability on the ridge-top site, the Black Death, the reduced military importance of the castle in the latter half of the fourteenth century, and significant damage to the town done by rebels in 1444, all contributed to progressive depopulation, so that by 1445 only 20 burgages remained occupied, and a mere handful were rent-paying a century later, by which time the castle was ruinous.
Because Caus declined to the point where, in the post-medieval period, none of its houses remained standing, and there was almost no subsequent resettlement, above-ground features of the town have entirely disappeared. This includes the chapel of St. Margaret's, built by Thomas Corbet in 1272, Caus having no church of its own, being part of the parish of Westbury. Though we hear in 1447 of a Castle Street and St. Margaret Street, we do not know exactly where these lay or whether either was a market-street. The line of the urban defensive enclosure indicates burgages would have been laid out to the north-west of the castle, along a street linking the castle to a northeast-southwest through road.
