The first land reclamation was undertaken by Peter Stuyvesant upon taking over as the colony's governor in 1646. Hoping to facilitate waste disposal and transportation, he organized the excavation of the canal along what is now Broad St. Back then, this was still called New Amsterdam, and the Dutch were great believers in canals.
By the American Revolution, the city's population had grown to 30,000, and land had become scarce and cramped in the city center. That's when the city began to sell 'water lots', wherein entrepreneurs would seek to use landfill to create additional lots for use.
The most recent landfilled area led to the creation of Battery Park City, built in the 70's on the earth excavated from the World Trade Center's foundation.