Developing solutions to current environmental crises depends on understanding through the historical record how the planet attained its current state. Since first European settlement in 1788 parts of the Sydney estuary (Port Jackson. Middle Harbour, Lane Cove River and the Parramatta River) have been substantially modified by dredging and foreshore reclamation, activities with significant environmental implications. Dredging in particular took place over a period of more than 140 years, removing as much as 100M tonnes of material from the estuary and redistributing it in reclamation sites or offshore. Investigation of the history of dredging in the estuary reveals major gaps in the records, with even basic information on gross annual expenditure and quantities not available through periods of major dredging works.