The largest commercial port between Southampton and Dover, the largest in Sussex and the nearest on the southern coast to London, Shoreham missed out on the growth that tourism brought to many of its neighbours. Instead, Shoreham has relied on trade from the sea and was an important port as far back as Roman times. Stretching three miles to the border of Hove, shingle spits formed over the centuries creating an inland lagoon, which provided the perfect basis for the development of a harbour.

A once thriving oyster industry was destroyed by pollution, although the decline had started during the Crimean War due to the lack of labour.

The town first developed 1 mile (1.6km) from the mouth of the River Adur and the Normans rebuilt the Saxon church soon after their Conquest. This is now known as the old town and there are a number of attractive buildings around the church.
The continued silting up of the estuary caused the Normans to move closer to the sea within 40 years of arriving, creating New Shoreham and building a second Church. The de Braose family who ruled the area from Bramber Castle probably ordered the move in around 1110. Ever since that time, the mouth of the river moved and was only fixed as recently as 1818.

The nearby Wooden Bridge was originally a toll bridge linking Old Shoreham to Shoreham Airport. Built in 1781, it was the main A27 crossing point over the river until as recently as 1971. It was rebuilt at this time although it no longer carries vehicular traffic.

When Richard I died in 1199, King John returned to claim the throne, landing here at Shoreham. This is also thought to have been the departure point of Charles II when he fled the country to France in 1651.