The town, originally named Durnovaria was founded by the Romans in AD 70. Two miles southwest of the town centre is the pre-Roman hill fort Maiden Castle, and the foundations of a Roman house are freely accesible near county hall. There are many Roman finds in the county museum.
Dorchester has been the County town of Dorset since 1305.
In the 17th cetury the town was at the centre of the Puritan emigration to America, and local rector John White organised the settlement of Dorchester, Massachusetts. The town was heavily defended against the Royalists in the English Civil War.
In 1685 the Duke of Monmouth failed in his invasion attempt, and almost 300 of his men were condemned to death or transportation in Judge Jeffrey's "Bloody Assizes" in Dorchester. In the 17th and 18th centuries a number of fires destroyed large parts of the town, but Judge Jeffrey's lodgings can still be found in the town.
On the hills to the south east of the town a large monument to a different Hardy (Sir Thomas Masterman Hardy, who served with Horatio Nelson) looks out over Dorchester, Weymouth, the Isle of Portland and Chesil Beach.
A market is held in the town on Wednesdays and Sundays.
The town has two stations linking to London, Southampton and Bristol.
Prince Charles has recently built the self-contained village of Poundbury on the eastern suburbs of the town.
" a man might as well spend time in Dorchester as in any town in England". -- Daniel Defoe