The topography of central Seattle was radically altered by a series of regrades in the city's first century of urban settlement, in what might have been the largest such alteration of urban terrain at the time.
When European settlers first came to Seattle in the early 1850s, the tides of Elliott Bay lapped at the base of Beacon Hill. The original location of the settlement that became Seattle - today's Pioneer Square - was a low-lying island. A series of regrades leveled paths for roads, demolished Denny Hill, and turned much of Jackson Hill (a remnant of which remains along Main Street in the International District) into a near-canyon between First and Beacon Hills. The roughly 50,000,000 short tons (45,400,000 t) of earth from these 60 regrades provided landfill for the city's waterfront and the industrial/commercial neighborhood now known as SoDo, and built Harbor Island, at the time the largest man-made island in the world.