Old Shoreham, the original settlement, sits a little way up the Adur from the sea and dates back to pre-Roman times; by the Domesday survey of 1086 it was an established village. Its church of St Nicolas — St Nicolas being the patron saint of sailors — is partly Anglo-Saxon in fabric, one of the older churches in Sussex, and reflects the antiquity of the upriver settlement.
New Shoreham was founded at the river mouth toward the end of the eleventh century by William de Braose, the first Lord of Bramber, who recognised the strategic value of the Adur estuary and its short crossing to Normandy. The new port town was laid out on a grid pattern that survives in essence in the present town centre, and was provided with a great cruciform church, St Mary de Haura — the name a contraction of St Mary of the Haven (or Harbour) — founded around 1096 and built in the decade following 1103. The original church was on a scale befitting the port's medieval importance, large enough to have been described as collegiate; the surviving building, Grade I listed, is the eastern half of the original, the great Norman nave having fallen into ruin by the time of the Civil War.
The medieval port of Shoreham was, for a period, one of the most important on the south coast: a centre of cross-Channel trade and a significant naval embarkation point. It was from Shoreham that the future King Charles II is traditionally held to have escaped to France in October 1651, after his defeat at the Battle of Worcester — the final leg of the journey commemorated in the long-distance footpath, Monarch's Way, that ends at the town. The port's fortunes fluctuated with the silting and shifting of the Adur's mouth over the centuries, requiring repeated re-engineering of the harbour entrance to keep the port viable.
The Marlipins, on the High Street — a twelfth-to-thirteenth-century building distinguished by the striking chequerboard pattern of limestone and flint on its façade — is one of the oldest surviving secular (non-religious) buildings in Britain. Its original function is uncertain; it was in use as an oat market by 1347, and may have served as a customs house for the port. It has housed a museum of Shoreham's maritime and local history, run by the Sussex Archaeological Society, since the 1920s.
Shoreham grew substantially in the Victorian period as a centre of shipbuilding and coastal trade, and the commercial harbour was progressively modernised through the nineteenth and twentieth centuries into the locked, sea-walled commercial port that operates today. Shoreham Fort, at the harbour mouth, is a Palmerston fort built in 1857 against the perceived threat of invasion under Napoleon III. In the early twentieth century, the shingle of Shoreham Beach became Bungalow Town, a settlement of converted railway carriages and a flourishing early British film industry — the locality was briefly known as ‘Hollywood on Sea’ — before the film studios moved away and the area was redeveloped for housing.
Shoreham Airport, on the Adur floodplain west of the town, opened in 1910 and is generally recognised as the oldest purpose-built commercial airport in the United Kingdom; its elegant Art Deco terminal building, opened in 1936, is a Grade II* listed landmark and a frequent filming location for period productions.
On the night of 15–16 October 1987, the south of England was struck by the Great Storm — the most destructive extratropical cyclone to affect the country since the Great Storm of 1703. Hurricane-force winds, gusting to over 100 knots on the exposed south coast, swept inland across Sussex, Kent and the home counties. The Met Office had not forecast the storm's severity; eighteen people died across southern England in a single night, and an estimated fifteen million trees were felled.
Shoreham-by-Sea, directly on the coast in the storm's path, was among the worst-affected towns in West Sussex. The harbour and seafront sustained extensive damage; the railway line was blocked; the town was, like much of the south coast, days recovering its basic services. The storm is, by some distance, the most significant single event in the modern history of the town — and the meteorological context into which, in the Book of Thoth Saga, the loss of Shoreham Haven Hospital was folded.