Chance finds and archaeological excavations to the north of the present town have revealed that early peoples passed through this valley. Stone Age artefacts have been discovered; during the Bronze Age a cremation cemetery was created here; traces of Iron Age habitations have been uncovered; two Roman farms have been excavated while small Roman artefacts have been found throughout the town. Early Saxon burials have also been unearthed but written history dates from the year 890 when Guthrum the Danish leader died and was buried at his royal town of Hadleigh.
In 991, Earldorman Brythnoth bequeathed the Manor of Hadleigh to the Priory Church of Canterbury Cathedral and thus began Hadleigh's status as a peculiar of the archbishop, which lasted until 1838. The rectory was in the archbishop's personal gift and several incumbents became bishops. At the reformation of 16th century Rowland Taylor and his curate Richard Yeoman were burnt here for their beliefs.
Hadleigh received its market charger in 1252 and 1438 administration was passed from manorial control to trustee's the market was sold to Babergh District Council in the late 20th century.
Throughout the medieval period and into the 17th century, woollen cloth was produced here, making Hadleigh one of the wealthier town in the country. These riches are exhibited in the houses that were erected in this period, many of which can still be seen in the main streets. In 1618, borough status was achieved but this was lost in 1685 owing to maladministration. At the same time, decline in the cloth industry brought great poverty. However, an economic revival during the Victorian period, encouraged partly by the coming of the railway in 1847, saw new development, while some older properties were re-fronted. Thus many buildings although appearing to be 19th century in date, owe their origins to medieval craftsmen.
The buildings of Hadleigh exhibit a variety of architectural styles that represent seven centuries of living and working in the community with 250 listed for their historical interest. The oldest part of the town consists of the High Street with Bridge Street to the North, Angel Street, George Street and Station Road to the East, Benton Street to the South, and, to the West, all the streets and lanes around the churchyard and market.