Regrading in Seattle

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.

The heart of Seattle, largest city in the state of Washington, is on an isthmus between the city's chief harbor—the saltwater Elliott Bay (an inlet of Puget Sound)—and the fresh water of Lake Washington. Capitol Hill, First Hill, and Beacon Hill collectively constitute a ridge along this isthmus (see Seven hills of Seattle). In addition, at the time the city was founded, the steep Denny Hill stood in the area now known as Belltown or the Denny Regrade.

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.

Seattle's first 58 regrades "consisted largely of cutting the tops off high places and dumping the dirt into low places and onto the beach". The most dramatic result of this was along that former beach, filling the land that constitutes today's Central Waterfront. Today's Western Avenue and Alaskan Way lie on this landfill.

These informal regrades came to an end around 1900; later regrades typically required changes to areas that had already undergone some development. City engineer R.H. Thomson established his prestige in 1900. He successfully provided the city with ample fresh water by running a pipeline from the Cedar River. He then undertook to level the extreme hills that rose south and north of the bustling city center. A central concern of Thomson's work in Seattle was to connect disparate parts of the city together, allowing easier movement. Thomson was quoted as saying that the city had developed the land "with but little regard as to whether the streets could ever be used or not, the main idea being, apparently, to sell the lots."

The first, unsuccessful, attempt to pierce the Capitol Hill – First Hill – Beacon Hill ridge came at the end of this era of informal regrades. In 1895, former territorial governor Eugene Semple (1840–1908) proposed several ambitious plans to reengineer Seattle. One of these, which he undertook in 1901, was to dig a canal from Elliott Bay to Lake Washington by cutting through Beacon Hill in roughly the area of Spokane Street, sluicing earth into the tide flats. His effort was defeated by unstable soils, which caused several cave-ins, and by the legal and political maneuvering of Judge Thomas Burke and others aligned with the Great Northern Railway. The Lake Washington Ship Canal ultimately followed the route north of downtown favored by Burke, taking advantage of existing lakes and bays. Semple left behind a canyon that is now used by the Spokane Street interchange on Interstate 5.

Thomson resumed the work of cutting through Beacon Hill to connect central Seattle to the Rainier Valley, the first of his major regrades, but he made his cut farther north. The Jackson Regrade between 1907 and 1910 slashed 85 feet (25.9 m) from the hill, requiring the demolition of the public South School and the original Holy Names Academy but providing fill for the tide flats below Beacon Hill that stretched south from King Street, filling in today's SoDo. Jackson Street became a slow slope upward from Elliott Bay in the west to the Central District east of the Capitol Hill – First Hill – Beacon Hill ridge.

Shortly afterward, just south of the Jackson Regrade, the Dearborn Street Regrade made an even deeper cut through the ridge. In one place, the level of the land was lowered by 108 feet (32.9 m); 1.6 million cubic yards (1,223,288 m³) of earth were moved. As with Semple's abandoned canal, there were several landslides, and many homes were destroyed that were not originally planned to be removed.