Two pipelines in Slapton have turned up evidence of Iron Age and Roman activity. One Iron Age pit and four Roman ditches were found on the Kingsbury to Buncefield pipeline along with pottery and brick of both periods. More Roman pottery was found in a pipeline south of Whaddon Farm.
The medieval history of the village is better documented. There are thirteenth century records of a watermill and fifteenth century records of Slapton Bridge. Slapton, Horton and South Whaddon manors were separate in the medieval period. There are also some medieval earthworks visible on aerial photographs in the fields south of Slaptonbury Mill, which look like house platforms and an enclosure. There are other earthworks around Whaddon Farm that suggest this was a larger settlement in the medieval to post-medieval period.
The only surviving medieval building is Holy Cross church with its fourteenth century nave and aisles and fifteenth century tower, though the chancel was rebuilt in the nineteenth century. There are records that Slaptonbury Farm was a medieval or early post-medieval house, but it was demolished in the nineteenth century. Similarly Horton Hall may have been a medieval house with its own moat and chapel and it had a medieval dovecote in the grounds but it was also demolished in the nineteenth century. Otherwise, the oldest secular buildings are Lanthorn Cottage, which is though to be sixteenth century, with King’s Head Cottage and the Carpenter’s Arms both being seventeenth century.
Much of the later history of Slapton that has shaped the settlement relates to the nineteenth century Grand Junction or Union Canal with its lock, lock-keeper’s cottage, bridge and pumping station. No doubt the nineteenth century coprolite workings known from historic documents relied on the canal to transport products.