Jessop, William (1745–1814), civil engineer, was born 23 January 1745 in Devonport, Plymouth, Devon, eldest child among two sons and a daughter of Josias Jessop, naval shipwright, and Elizabeth Jessop (née Foot). His modest circumstances might have precluded meteoric advancement in Georgian society, but William Jessop was fortunate to attend a local school where his intellectual and mechanical genii were encouraged. He benefited by his attractive personality and his father's faithful upkeep of John Rudyerd's Eddystone lighthouse facing Plymouth Sound. Indeed, for its replacement (1756–9) by John Smeaton, he was appointed the builder.
Smeaton, whose new lighthouse became an international model, adopted William as his pupil in 1759. This meant migration to Smeaton's estate near Leeds in distant Yorkshire. Jessop, whose father died in 1761 and whose mother was hard pressed to afford his education, was supported by Robert Weston, a shareholder in the old Eddystone lighthouse. Such was the professional respect of these men for the Jessop family that every means was found to promote William's career. In turn he worked hard to prove his worth. Smeaton employed him as his professional assistant in 1767 when his apprenticeship had ended.
Jessop's special abilities lay in river navigation, canal-building, harbours, and quays, which he had studied closely in Yorkshire. The north of England in the early industrial revolution was the perfect learning environment, and Jessop soon understood both the logistics of commercial transport and the geology of the industrial landscape, essential knowledge in avoiding expensive mistakes. Smeaton had great confidence in him, handing him all the difficult practical challenges of inland waterways, including the financial estimates. Jessop soon emerged from the shadow of his master: in 1772 he went out on his own but remained closely associated with Smeaton.
In 1773 Jessop and Smeaton travelled together to Ireland, where they observed works by the recently formed Grand Canal Company, to which Smeaton had been asked to provide assistance. After thorough examination of work in progress (little had in fact been achieved by successive undertakers since 1756) to connect the River Shannon at Shannon Harbour near Banagher, King's Co. (Offaly), with Dublin, Jessop carried out surveys for Smeaton to prepare him for assisting in the completion stages. He also visited the Tyrone coal canal, seeking the best design options for its ‘hurries’, artificial slopes for rolling or sliding boats to lower levels of the canal without the use of standard locks. For this he and Smeaton seem to have favoured a wheeled cradle, and the use of traction by a horse gin on upward slopes.
On completion, Jessop resumed his canal- and dock-building business in England, rapidly reaching the top of his profession. In 1774 he became secretary of the Smeatonian Society, a civil engineering body named in honour of his mentor. He simultaneously obtained appointments to the most prestigious canal projects in Britain, extending from the north through the midlands into southern England and Wales. His works included exhaustive preparations to extract from parliament legislation for each of his many waterways, and to erect precipitous aqueducts over valleys and tunnel through solid rock; the same hard graft and energy with which railway pioneers would brashly replace his achievements some decades later.
Jessop's second Irish tour (1785) witnessed some improvements inland on the Grand Canal, including a branch south to the River Barrow at Monasterevan. He explored a proposed ‘circular line’ canal to link the Dublin terminus of the Grand Canal (near James's St.) with the mouth of the Liffey at Ringsend. He approved the proposal and suggested provision of a small basin at its exit (adjoining the mouth of the River Dodder) to facilitate barges awaiting transfer of goods to ships at Ringsend. This plan gave way in 1791 to Jessop's more ambitious project at the same site: as consulting engineer to the company (1790–1802) he was asked to design the Grand Canal docks, a full-scale facility for hundreds of vessels, dry-dock maintenance (three graving docks), a wet dock, and entrance locks and quays named after the Hanoverian royal dynasty, all around two large basins. Jessop made periodic site visits, and construction, including the circular line (1790–93), was completed in 1796. It was a grand memorial to Jessop, but already destined for obscurity as the commercial focus of Dublin port moved further north. Pressing westward to the Shannon, he overcame the waterlogged midland bogs by draining the canal route along its sides, creating a broad embankment into which he dug a channel packed with watertight puddle clay. Jessop encountered particular difficulty in the Bog of Allen near Edenderry, King's Co., but given the near-absence of surface geology, his achievement was remarkable. In addition, he surveyed the Shannon itself from Lough Allen to Lough Derg to reassure the Grand Canal Co. of its navigability. In addition, he was fully occupied with British contracts including early horse-drawn railways, London's West India Docks (on the Isle of Dogs), and the Grand Junction (Grand Union) and City canals, and increasingly undertook Scottish projects, balancing these with his Grand Canal consultancy and advisory role on other Irish projects.
Accordingly, in the 1790s he was consulted on the erratic progress of the Royal Canal north of Dublin city centre and on the ballast board's proposals for a Pigeon House harbour near Ringsend. In 1800 he outlined to the ballast board his Dunleary (Dún Laoghaire) harbour proposals, with the inclusion of a ship canal between the harbour and the Grand Canal docks. Jessop's last Irish engagement was in 1806 on the Barrow river navigation, an extension of the Grand Canal branch to Athy, Co. Kildare. As he had become known as a pioneer of the iron railway, he was approached by the Grand Canal Co. to provide estimates, but declined. Much work yet lay ahead of him in Britain.
Throughout his career Jessop was associated with leading British and Irish engineers. He undertook prodigious professional commitments but relied upon resident engineers where necessary. He was for many years an alderman of Newark (in Nottinghamshire) and once its mayor. He even managed to have a home and family life, marrying (1777) Sarah Sawyer of Haddlesey House, Yorkshire, with whom he had seven sons and one daughter. Living at first in Yorkshire, they eventually moved to Butterly Hall, Derbyshire. William Jessop died 18 November 1814 after two years of ill health and was buried in Pentrich churchyard, where his wife was also buried in 1816. Several portraits exist, one at the National Portrait Gallery, London.