The River Mersey begins in Stockport with the confluence of the River Tame and River Goyt and flows 70 miles to the Irish Sea. The River Mersey has the second highest tidal range in the UK, varying from 4m at neaps to 10m at spring tides. The river flow is about 1% of the tidal flow.

During earlier times, the tides and winter gales would probably have been too severe for Roman and Anglo-Norman ships, but a hamlet, Liverpool, developed around the pool for spring and summer use. The name Liverpool is thought to have been derived from the Anglo-Norman translation from Latin, meaning ‘spring-time anchorage’. Liverpool was granted its first Royal Charter in 1207 by King John, for the development of the town. Growth, however, was slow until the 18th century.

In 1717 Thomas Steers built several docks at Liverpool, as well as St George’s Church, the Old Ropery Theatre and several other buildings. Steers also built a dry dock and a new pier, and the shipbuilding and repairing businesses, which had developed around the docks, were moved further afield. Thomas Steers was also responsible for the fortification of Liverpool in 1745, during the Jacobite rebellion.

Trade developed with the Americas and the West Indies, and Liverpool became the second most important port in Britain. Goods from Liverpool, which included Cheshire salt, Lancashire coal and textiles, Staffordshire pottery and Birmingham metal goods, were exchanged for slaves from West Africa, who were in turn traded for sugar, spices, molasses and plantain crops from the West Indies. This was known as the Liverpool triangle during one of Liverpool’s less worthy periods of history. More information on this topic, and others associated with Liverpool’s seafaring history can be obtained from the Merseyside Maritime Museum.

Of particular interest to the National Oceanography Centre in Liverpool (formerly the Proudman Oceanographic Laboratory) are the recently discovered and investigated tidal records kept by William Hutchinson (1715–1801). This remarkable man was, amongst many other things, Harbourmaster at the Old Dock at Liverpool, living a mere 14 yards from the dock gates. He took it upon himself to note the height of every high water between 1768 and 1793 and also included the times of the high waters for seven of those years. This makes Liverpool the first British location at which systematic tidal records were kept, and is an invaluable data set, which has been the subject of a recent study by Dr Philip Woodworth at the Proudman Oceanographic Laboratory. William Hutchinson started his working career as a common sailor, and progressed to diverse roles as a privateer captain, a ship owner, boat builder, commercial trader, author and philanthropist. He was made a Freeman of Liverpool in 1755 for the contribution he made to the fishing industry by fitting out cod boats. Hutchinson was instrumental in the establishment of the world’s first lifeboat service at Formby and also the Mersey pilotage service. His many inventions included items of marine equipment and armoury. He also had a keen interest in reflecting mirrors and invented both the reflecting mirror and the oil burning apparatus for the first of the two lighthouses built on top of Bidston Hill, in the grounds of Bidston Observatory.

Facing Liverpool, on the opposite bank, a Benedictine Priory was founded between 1154 and 1199, and was the beginning of the development of Birkenhead. The name is thought to derive from bircen head, meaning ‘on a birch covered headland’, or else it refers to the position at the mouth of the River Birket. The monks of the Priory introduced the first ferry service across the Mersey from their Priory to Liverpool. During bad weather, travellers would be accommodated at the Priory, and slowly the population around the Priory developed, providing services to the monks and the travellers. The Priory was closed in 1536, on the orders of Henry VIII, but in recent years has re-opened as a tourist attraction. During the early nineteenth century, steam ferries were introduced across the Mersey. There followed a programme of dock building and the construction, in 1861, of a floating landing stage at Liverpool. The shipbuilding industry developed, along with others, notably flour milling and soap manufacturing. Merchants working in Liverpool realised that they could commute from Wirral, so dormitory towns such as Wallasey developed. Eventually a railway was constructed under the river, followed by two road tunnels.

New Brighton, on the Birkenhead side of the river, began to develop in 1830, as the potential of a seaside resort on the doorstep of Liverpool began to be realised. Co-incidentally a fort was built on the rocks at New Brighton, Fort Perch Rock, for protection against any invasions. The name was taken from a wooden perch which was built at the spot in the 1690s to warn passing ships of the dangers of the sandstone rocks nearby. The Fort originally had sixteen 32-pound cannons facing the sea and two 18-pound cannons which were intended to be used to defend the fort from attack from the land. The fort was modified and upgraded several times over the years, but a shot was never fired in anger. It is now a tourist attraction.

The decline in the water quality of the river system began in the early 19th century with the rapid expansion of the textile industry in Lancashire. This growth resulted in an increase in the dyeing and bleaching industries. Vast quantities of water were required for the chemical industries, more people moved into the area to become involved with the manufacturing processes, and more domestic water was required by the population, resulting in more effluent being discharged into the river. The river fishing industry rapidly declined and by the mid-19th century the state of Britain’s rivers, and particularly the Mersey, was a cause for serious concern. During the 1950s and 1960s a number of Acts of Parliament were introduced to control the discharge of harmful waste into rivers. In the early 1980s a project specifically for the Mersey basin was proposed, leading to the formation of the Mersey Basin Campaign. This has been extremely successful, with the River Mersey now becoming one of the most improved rivers, with fish and other wildlife steadily returning.

In 1894 the Manchester Ship Canal, which connects the River Mersey and Manchester was opened. This is the only canal in Britain that can take ocean-going vessels.

By the late 1950s, the docks had started their decline. Ocean-going passenger liners lost much of their custom to airliners, and changes in cargo handling meant that one new container vessel could replace six traditional cargo liners. Competition grew from new container ports such as Felixstowe, and local difficulties developed.

The regeneration of dockland areas on both sides of the Mersey were largely led by the Merseyside Development Corporation (1981–1998). Tourism now makes a major contribution to the fortunes of Liverpool.

In recent years there has been a great deal of improvement to the embankment system on the Wirral banks of the River Mersey, instigated by the Metropolitan Borough of Wirral.