There were many Celtic settlements in the area in prehistoric times, as can be found all over Dartmoor, which still has the highest concentration of ancient sites in Europe. One of these sites, Bury Down, (meaning "Earth Work on the Hill") gave it's name to Boringdon. The workings would have been a defence against the Danes who would sail right up to Plympton. The castle was of premier importance when a contingent was sent from the castle to repel the Danes at Wembury in 851. Plympton Castle has had a fairly torrid history. It stands on what was probably the country's earliest British settlement. A contingent from the castle helped repel the Danes at Wembury in 851. Little resistance was offered to William the Conqueror, and It was under seige by the Sherriff of Devon under the reign of Henry III. It is unsure as to when it was actually put into the state of ruin it now stands, although it is probably due to the seige of Baldwin de Redvers by the Sherriff. However it is recorded that it was a ruin in the 16th century.

The priors of Plympton were very powerful Abbots, who lived in the Priory which was situated behind the present St Mary's Church. They were great Land Owners, and were dated back to the 9th century, when the Saxons established the Monastery. King Egbert on Conquering West Wales in the 9th century, (as the area was known then), for his kingdom of Wessex, decided that he wanted to keep Plympton for himself, and it wasn't much later then the Priory was founded. There is great mystery over all the events that occurred at the priory, but one thing is for sure, it lasted until 1539 when Henry VIII's commissioners dissolved the Monastery. However what is known about the Abbots is facisinating. They held great power over rural Devon, and were responsible for creating The Abbots Way, which is a footpath that ran from Plympton up to Princetown on Dartmoor and was used by the Monks to Inspect their lands there. The path still exists today, however development has destroyed the start of the path, it can still be followed for a long way on Dartmoor, and links up with the Two Moors way, which was also used by the Abbots. The prior held many titles as right, such as Lord Mayor of Sutton, and could draw a tithe from most of the area covered by modern day Plymouth and parts of Exeter. These rights were unpopular with residents of these areas, and the Prior resisted the efforts of the people of Sutton to gain a charter. He eventually relented in 1439, which led to the town of Plymouth coming into existence

The Saxon Monastery was originally a college of secular canons, but was converted to an Augustinian priory by the Bishop of Exeter with the permission of Henry I. The original college were succeeded by an ornate Norman priory. Little is known of the buildings, but it is believed that there was a large tower present at one time, due to the prescense of Tower house, which is one of the dwellings that still remain to this day. It was custom for important people to stay at the priory whilst on their way to France and Spain. Edward the Black Prince was entertained by the Prior in 1348. The modern day school called Old Priory is a direct reference to the Abbots, whilst all that remains of the priory is a doorway in St Mary's Church grounds.

Plympton was recorded in the Doomsday book, during the survey of lands conquered by Wlliam the Conqueror in 1068. The manor consisted of 2 hides, 2 virgates roughly 1686 acres, divided between the Lord and the Villagers equally, and valued at £13.10 shillings. The doomsday demense consisted of land for 2 ploughs, 160 acres of arable, 6 acres of meadow and 20 of pasture, the remaining acres were taken by the cattle and precincts Once the Normans had settled Tin was mined in greater quantities on Dartmoor, and the Town started to flourish, with St Maurice becoming a very important trading port, whilst St Mary had to wait for the coming of rail to prosper better than St Maurice.

THE KINGS LANDS (honour of Plympton) ANCIENT CROWN LORDSHIP. PLINTONA (Plymholme, consisting of Plympton St Mary or Herdwick Manor, and Plympton St Maurice alias Plympton Earl, The Lordship of the same.)

Plympton St Maurice was originally called St Thomas, although when the name changed was uncertain, but it changed between St Maurice and St Thomas several times before St Maurice became more generally used. It was much smaller than St Mary being only 200 acres, however it was very much more prosperous due to the Tin trade, and has a lot more interesting early history. St Maurice prospered in those early days, and the first school in Devon was built there, Plympton Grammar School, in a building that is still in a very good state of preserve. It was in the Rectory of the school that the Artist Sir Joshua Reynolds was born in 1723

The town became a borough in the 12th century, and from 1259 elected two members of Parliament. It was designated a Stannary Town in 1328, and miners from Southern Dartmoor were required to bring their ingots to a tin court in Fore street for testing and weighing. One of the Major reasons for this was the deep river which came up to the foot of the Castle. This allowed ships to take the Tin straight from Fore Street to their destinations world wide. During the 13th and 14th century, Plympton St Maurice was bigger than Plymouth and far more important as a port. There is an old ryhme which states that "When Plympton was a Busy Vale, Plymouth was a fuzzy dale". However the life blood of Plympton soon became it's poison, as the Tin Mines on Dartmoor produced a lot of silt which was was down stream, this caused the river to silt up, and took away the port. There is little evidence of the fact that there was a port here nowadays, except for the street names and the mooring points around Fore Street. The whole area of Valley road, which includes several football pitches lies on top of what was water 600 years ago.

The history of Plympton St Mary is not as colourful as St Maurice due to the parish having more of a religious worth, and little else in it's early years. The fact that the river went right past and into St Maurice was also a factor in the parish having less significance, in early times. Plympton St Mary was established by the old priors of Plympton, and is made up of the Villages of Ridgeway, Underwood and Colebrook, but also included the hamlets of Hemerdon, Sparkwell and Venton. A major part of St Marys was the 7 estates which were also a major part, but most have long since vanished. The Estates of Saltram, (Now a national Trust house), Newnham Park, (still an estate, but much smaller, and mainly used for events such as the mountain bike championship) Boringdon, (now a hotel), and Chaddlewood, (now flats) being the most prominent.

The Cholera epidemic of 1832 was well recorded with 30 people from Underwood, with only around 300 population, dying. There is a mass un marked grave in the churchyard for all the victims of the epidemic. The Reverend William Coppard kept a diary throughout this time, and visited many parishoners who were struck down. The disease was a result of some squalid conditions, Coppard recorded that William Parsons lived with his wife and five children in a room 14 feet by 16, and containing only two beds. The condition of the room was appalling, and Coppard arranged for a Mason to clear the drains and whitewash the walls to provide a more hygenic surrounding. Many weird conclutions were used to beat the epidemic, and many neighbours put themselves at great risk to give life saving blood transfusions to the sick. The epidemic was over by October of that year, and a Slate headstone was put on the Graves of the victims, bearing just one inscription - 1832.

The Cholera epidemic highlighted some of the poverty in a town which was really fairly affluent as a whole, and was home to 3,000 people, however these were very spread out, with the Parish having over 10,000 acres. However in it's early years it was overshadowed by Plympton Earl, (as St Maurice was, and still is in council terms, known), which was the Tin trade as a major industry. However as years have progressed, the greater lands of St Mary have proved to be more beneficial as it now hosts most of the Industry and shopping areas On top of the Hill leading to Plymbridge stands the Triumphal Arch, which was the gateway between Boringdon and Saltram, and was a feature to show off the wealth the town had in the 18th century.