Horndon is thought to be the location of an eleventh-century Saxon mint, one of only three known in Essex. At that time it was policy to disperse coin manufacture, both to ensure minimum disruption should one centre cease production and to achieve maximum disruption of the coinage (Eddy and Petchey, 1983). However, like other dispersed Saxon mints, it appears to have been short-lived. It has been suggested that a rectilinear field-system and substantial lynchets to the east of High Road are remains of a possible defended enclosure, presumably linked to the Saxon mint (Eddy, 1980).
Horndon was important in the medieval period as a collection point for wool which at the time of the Domesday survey was the principal product of the Essex coastal and riverine marshlands. It may have retained a market from the Saxon period; one was certainly held by 1281 (B.L. 5251), and a fair was granted in 1277 (Charter Rolls). Cloth manufacture is known to have started in the late fifteenth century; the Feet of Fines for 1502 referred to 16 messauges, 60 shops and 70 stalls in Horndon, and some of these shops may also represent workshops (Bingley, 1975-6). The sixteenth-century Market Hall was built for the wool trade. As well as the wool trade, sheep’ milk cheese was also a local commodity and the manors of Horndon had shares in a fishery. The town failed to develop in the later post-medieval period and remained little changed in plan from that of the medieval period. The medieval and post-medieval town consists of the High Road with the village strung out along it, the church which is set back to the west and a possible infilled market-place sited between the church and High Road.