Trowbridge lies on a ridge aligned southwest/northeast, cut through by the River Biss, which connects to the Avon; Bradford-on-Avon is only a couple of miles away. The most important road running through it connected Devizes and the Somerset borough of Wells. Domesday mentions Trowle as held by a prominent Anglo-Saxon family; it is later seen as part of the parish of Trow(le)bridge. The tenant of Trowle also held Straburg, and the two holdings remained thus associated within the parish as they changed hands, it is usually suspected that Straburg was the derivation of Trowbridge. The precise location of these Domesday properties remains unknown, but they show no signs of being more than modest agricultural settlements in 1086.
Whether the 'burg' of Straburg derives from burh or bridge is uncertain, but the latter is more likely. The Biss was not deep and could be forded, yet the location of a secondary entrance to the castle was adjacent to the site of the later town bridge; so there may well have been a bridge there at the time the castle was built, though probably not earlier, as the site of the town bridge must have been dictated by the castle layout. An older bridge or ford may have been at the foot of the descent from the ridge-top to the river, subsequently blocked by the castle complex, forcing the downward route to divert. This possibility was given some support by archaeologists' discovery of a Saxon settlement on a commanding position atop the ridge, across much the same area where the castle was later built. The settlement originated in the seventh century and was provided in the tenth with a stone church with ditch-surrounded cemetery. In the first half of the eleventh century was established a manor-house with substantial ditch-bank enclosure, its sole entrance adjacent to the church; this was probably the home of the family identified as owners in Domesday, and it overwrote part of the existing village. Further contemporary settlement was identified to the north-west, and might conceivably have spread around the enclosure.
In 1100 Trowbridge was held by Edward of Salisbury, sheriff of Wiltshire (ca.1081-1105); his daughter Matilda married Humphrey de Bohun, who became lord of Trowbridge by right of his wife, and they founded the famous family whose members became earls of Hereford and of Essex in the thirteenth and fourteenth centuries, while Matilda's brother sired a line of earls of Salisbury. It must have been their son, Humphrey II (d.1164), who built the castle at Trowbridge, first mentioned in 1139 when it withstood a siege, although its military consequence did not outlast the civil war that necessitated it. Trowbridge descended to Humphrey II's grandson, Henry de Bohun, as did the earldom of Hereford and constableship of England; but as Henry was a minor at the time, he was not fully invested until King John's accession in 1199. Although his main focus may have been his estates in the Welsh Marches, the caput of Henry's estates was at Trowbridge and he had an interest in developing it, and holding on to it. However, after he joined John's baronial opponents, his estates were declared forfeit and John gave them to his half-brother, William Longespée, earl of Salisbury and husband of Ela, descendant of Edward of Salisbury. The baronial victory and implementation of Magna Carta enabled Henry de Bohun to reclaim his manor (though not the castle), but in 1212 Longespée initiated a legal challenge to the territory, which dragged on until 1229 (after the deaths of both claimants), when a settlement between the parties saw the castle and manor of Trowbridge go to the Countess Ela, founder of Lacock. From her the manor passed down the Longespée line, then by marriage to other noble families.
Almost nothing remains of the castle, though it is remembered by Castle Street which runs through the former castle site. It stood on the south side of Trowbridge, bounded on the west by the Biss and on its other sides by a semi-circular moat which began near the bridge at the north end of the castle and followed the line within Fore Street (the later High Street) to eventually rejoin the Biss. The main entrance to the castle is thought to have been at the junction of Castle and Fore Streets. A good part of the prior Saxon village was torn down to make room for the castle bailey, and the manorial enclosure was also partly built over. The Saxon church and its now-reduced graveyard continued in use until around 1200. In the fourteenth century parts of first the ditch and later the bailey were being leased out for private use, probably for grazing livestock or for building. The absentee lords had lost interest in the castle, as they had in their manor-house, which also fell into disrepair.
We encounter references to burgesses and burgages in the late thirteenth and fourteenth centuries, the earliest being from a deed, probably dating to 1243, in the Lacock Abbey cartulary by which a goldsmith granted one of the burgages. The burgesses' main liability was a money rent and they had exemption from paying tolls and the right to pass on their tenements through devise. The number of the privileged tenements hovered just above the hundred mark in the late fourteenth century. Cloth manufacturing is evidenced at Trowbridge in that period; it may not then have been a major undertaking of the populace, though it was by the close of the Middle Ages. Leather-workers are also evidenced.
Henry de Bohun moved quickly, after becoming earl, to obtain in March1200 royal licence for a Tuesday market at Trowbridge and a July fair; these are the only commercial institutions he is known to have founded, nor was this a strategy much adopted by his descendants, although his grandson obtained a market licence for an existing town at Huntington (Herefords.). Trowbridge's marketplace receives a documentary mention in 1303, when the rental terms of stalls or shambles there were being reviewed; they were rented or leased not only to local residents but also to men from Bradford, Chippenham, and even from outside the county in 1375, for example, a Somerset man paid 4d. for an open space in the market. A Tolselde is heard of in 1372 and was not new then. Although there is no indication the burgesses of Trowbridge had their own institutions of self-government in the Middle Ages, administration being through the seigneurial court, among local officials referenced in the late medieval court rolls were cadaveratores whose duties included inspecting the meat sold by butchers in the marketplace, to ensure it was fit for consumption; they may also have had wider supervisory powers over market matters, as was later the case.
Although the Extensive Urban Survey report on Trowbridge has the new town laid out at the same time as the castle was built, it seems more likely that this development occurred in conjunction with the market grant; a market licence would not have been required had a thriving urban market been in existence before Henry II's time. Furthermore, as the report's author acknowledges, we do not even know if the original castle was constructed all in a single phase in the 1130s, or whether the outer bailey represents a later addition. Certainly the layout of the town assumes the castle complex had been completed. The marketplace was located beside the north-eastern stretch of the curving line of the castle ditch, along part of what was later the High Street, and with easy access from the castle's main entrance. Burgage plots were laid out on the higher ground of the ridge, the Biss being susceptible to flooding. The principal focus of this planned town was between the High Street and Back Street to its north (part of which was later named Church Street), the latter curving to parallel the ditch-hugging curve of the High Street. Other burgages may, the report suggests, have been situated: north of Back Street/Church Street; around Silver Street/Market Street, which run from the east end of Church Street down to the east end of the High Street marketplace; and around Hill Street, which connected Back Street and High Street at their west ends, in the vicinity of the bridge. The short Market Street appears a remnant of the east end of the original marketplace, indicative of the width of the large area laid out for the market, but later largely lost to encroachments, including the conversion of stalls and shambles into permanent structures. It is of course entirely conceivable that a village market had arisen following, or even before, the construction of the castle.
Henry de Bohun also had Trowbridge's Saxon church, which had remained in use within the inner bailey, turned over to secular uses (it was demolished in the sixteenth century), and a new church built within the planted town, between High Street and Back Street; this still contains some thirteenth century fabric, although is mostly of the late fourteenth and fifteenth centuries. This relocation of church and churchyard to a large new site would have been problematic had a planned town been in place prior to Henry's time; it was more probably an integral part of the plan for the new town. In the early twentieth century skeletons and twelfth-century tombstones discovered by excavations in Castle Street pointed to the location of the original church's cemetery. As the castle lost its fortress role, the town expanded into the bailey, giving rise to Castle Street (first mentioned 1386) and Court Lane (ca.1461). The planted town may also have expanded, in an unplanned fashion, north-eastwards, south of the castle along a stretch of Castle Street that led to another crossing of the Biss, and perhaps also around the town bridge north-west of the castle.
In 1295/96 the tolls from market and fair were calculated as about 32s. and in 1303/04 as £1 17s.5d., with by far the greater part of that from the market. In 1311, in the context of an inquisition post mortem on one of Trowbridge's lords, we hear of a Saturday market, which was the market-day in later times; it seems likely this represents a changed day rather than an additional one. The market's value was then estimated at 50s.annually (about 6% of the total income from the manor), while the profits from the manorial courts were valued at 56s.8d. Another such inquisition, in 1347, mentions the court profits, which had skyrocketed to £17 6s.8d.; but it says nothing of the market and likewise ignores that of Amesbury nor does a third extent taken in 1361. However, the revenues from market tolls and other profits are given by other sources; figures from 1349, 1356, and 1360 show a significant decline, and by 1372 the market was being farmed out for a mere 3s.4d, although the fair had recovered to its 1303 value. We must of course allow for the effects of plague on the economy, the proliferation of toll exemptions, and a gradual focusing of long-distance commerce onto larger or better-placed market centres; yet over much the same period Warminster's market profits were on the increase. In 1383 the fair profits dropped by about half, which was blamed on bad weather. Profits continued to be lacklustre into the fifteenth century, and both market and fairs were usually farmed out. Yet the renting and leasing out of market spaces to traders from adjacent counties suggests that Trowbridge's market remained viable as a location attracting buyers and sellers, even if not very profitable to its owner. The rebuilding of the church similarly suggests local prosperity in the Late Middle Ages. The fair continued to do well enough that it was held as late as the nineteenth century.