
The topography of central
Seattle
Seattle ( ) is the most populous city in the U.S. state of Washington and in the Pacific Northwest region of North America. With a population of 780,995 in 2024, it is the 18th-most populous city in the United States. The city is the cou ...
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
An isthmus (; : isthmuses or isthmi) is a narrow piece of land connecting two larger areas across an expanse of water by which they are otherwise separated. A tombolo is an isthmus that consists of a spit or bar, and a strait is the sea count ...
between the city's chief harbor—the saltwater
Elliott Bay
Elliott Bay is a part of the Central Basin region of Puget Sound. It is in the U.S. state of Washington, extending southeastward between West Point in the north and Alki Point in the south. Seattle was founded on this body of water in the 1850s ...
(an inlet of
Puget Sound
Puget Sound ( ; ) is a complex estuary, estuarine system of interconnected Marine habitat, marine waterways and basins located on the northwest coast of the U.S. state of Washington (state), Washington. As a part of the Salish Sea, the sound ...
)—and the fresh water of
Lake Washington
Lake Washington () is a large freshwater lake adjacent to the city of Seattle, Washington, United States.
It is the largest lake in King County, Washington, King County and the second largest natural lake in the state of Washington (state), Was ...
.
Capitol Hill
Capitol Hill is a neighborhoods in Washington, D.C., neighborhood in Washington, D.C., located in both the Northeast, Washington, D.C., Northeast and Southeast, Washington, D.C., Southeast quadrants. It is bounded by 14th Street SE & NE, F S ...
,
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 of earth from these 60 regrades provided
landfill
A landfill is a site for the disposal of waste materials. It is the oldest and most common form of waste disposal, although the systematic burial of waste with daily, intermediate and final covers only began in the 1940s. In the past, waste was ...
for the city's waterfront and the industrial/commercial neighborhood now known as
SoDo
Sodo () or officially Wolaita Sodo (, ) is a city in south Ethiopia. The city is a political and administrative center of the Wolaita Zone and South Ethiopia Regional State. It has a latitude and longitude of with an elevation between abov ...
, and built
Harbor Island, at the time the largest man-made island in the world.
Early years

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."
Cutting through Beacon Hill
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
The Lake Washington Ship Canal is a canal that runs through the city of Seattle and connects the fresh water body of Lake Washington to the salt water inland sea of Puget Sound. The Hiram M. Chittenden Locks accommodate the approximately diff ...
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
Interstate 5 (I-5) is the main north–south Interstate Highway System, Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels thro ...
.
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 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 ; 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.
The resulting gap at Dearborn Street was deep enough to require a bridge running roughly north-south. Originally known as the
12th Avenue South Bridge and now known as the Jose P. Rizal Bridge, it is now on the
National Register of Historic Places
The National Register of Historic Places (NRHP) is the Federal government of the United States, United States federal government's official United States National Register of Historic Places listings, list of sites, buildings, structures, Hist ...
.
File:Seattle 2nd Ave south from Pine Street 1880.jpg, Looking south from Pine Street on the south slope of Denny Hill, 1880. The wide bay at the foot of Beacon Hill is now the location of the SoDo neighborhood.
File:Seattle - Dearborn St regrade, 1912.gif, The Dearborn Regrade in progress, 1912. Looking west, towards the 12th Avenue South Bridge/Jose P. Rizal Bridge, constructed the previous year.
Denny Regrade

The Denny Regrade began before the Jackson and Dearborn Regrades, but the last stage was not completed until decades later. Before regrading, the much-admired Denny School
and the upmarket Washington Hotel stood atop the hill,
along with numerous residential buildings.
The two-storey high Denny School was found on Battery Street, between Fifth and Sixth Avenues, and was considered "handsome in the extreme."
City engineer
R.H. Thomson considered Denny Hill to be the biggest impediment to traveling to other places in the city. Although in retrospect it is referred to as the Denny Regrade (and the name has become the name of a neighborhood), there were, in fact, several separate regrades of the former Denny Hill, beginning with private-sector efforts. Around 1900, property owners along relatively low-lying First Avenue took it upon themselves to cut through from Pike Street to Cedar Street. A similar cut (but initiated by the City) lowered Second Avenue in 1904; around the same time, the south part of the hill was shaved off as Pike and Pine Streets were regraded between Second and Fifth Avenues.
The more dramatic Denny Regrade No. 1 (1908–1911) sluiced away the entire half of the hill closest to the waterfront, about 27 city blocks extending from Pine Street to Cedar Street and from Second to Fifth Avenues. of water a day were pumped from
Lake Union, to be aimed at the hill as jets of water, then run through tunnels to Elliott Bay.
Much of the motivation for the regrade had been to increase land values, but the area opened up—the heart of today's Belltown—was left as a strip cut off from much of the rest of the city by the remaining eastern half of the hill, whose western face offered no route of approach. Meanwhile, property-owners and investors hesitated to build on the remaining portion of the hill, because they considered it likely that their buildings would eventually be destroyed in the next phase of the regrading process, which was now well under way.
The result was Denny Regrade No. 2, begun in February 1929 and lasting 22 months. This time, the technology was power shovels rather than sluicing, with earth carried to the waterfront by
conveyor belt
A conveyor belt is the carrying medium of a belt conveyor system (often shortened to a belt conveyor). A belt conveyor system consists of two or more pulleys (sometimes referred to as drums), with a closed loop of carrying medium—the conveyor b ...
s, then placed on specially designed
scow
A scow is a smaller type of barge. Some scows are rigged as sailboat, sailing scows. In the 19th and early 20th centuries, scows carried cargo in coastal waters and inland waterways, having an advantage for navigating shallow water or small ha ...
s and dumped in deep water. The scows were intentionally designed to capsize in a controlled manner. They were symmetrical top-to-bottom and side to side; a
seacock could be opened to fill one side with water. In three minutes it would capsize, dump its load, bob up, empty the tank, and right itself.
One of the buildings demolished in Denny Regrade No. 2 was the Denny School on Battery Street between 5th and 6th Avenues. Opened in 1884, it had been described as "an architectural jewel... the finest schoolhouse on the West Coast".
While the 38 blocks were being regraded, the country entered the
Great Depression
The Great Depression was a severe global economic downturn from 1929 to 1939. The period was characterized by high rates of unemployment and poverty, drastic reductions in industrial production and international trade, and widespread bank and ...
, radically reducing the demand for land. Most of the new lots sat vacant into the 1940s; the area (especially east of Sixth Avenue) remained a
gray zone into the early 21st century, when it finally began to gain an urban or suburban identity as the west edge of the new growth of
South Lake Union.
Thomas Burke questioned the Denny Hill regrade, stating to a reporter at the closing party of the Washington Hotel that "from a commercial point of view, and certainly from an aesthetic one, it would have been much better to have saved Denny Hill by carrying Third Avenue under it, thus obtaining the desired result, while preserving in all aspects the natural beauty that means so much to any city."
Seattle megaprojects volume moved.png, Treemap comparing the volume of earth moved by the megaprojects that transformed the landscape in and around Seattle. The Denny and other regrades moved a combined total of more than 35 million cubic yards of earth. Creating Harbor Island involved 7 million cubic yards, while the Ballard Locks project moved 1.6 million, twice that of the Alaskan Way Viaduct replacement tunnel
The State Route 99 tunnel, also known as the Alaskan Way Viaduct replacement tunnel, is a bored highway tunnel in the city of Seattle, Washington, United States. The , double-decker tunnel carries a section of State Route 99 (SR 99) und ...
. Straightening the Duwamish River and filling its tideflats was the largest single project, at nearly 22 million cubic yards.
Denny Regrade-1.jpg, Denny Regrade No. 1 in progress, circa 1910
Seattle - Denny School - 1900.jpg, The 1884 Denny School (depicted here in 1900) on Battery Street between Fifth & Sixth Avenues was demolished in 1928, one of many major buildings demolished as part of Denny Regrade No. 2.
Notes
References
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Further reading
* ''Emerald City: an environmental history of Seattle'', Klingle, Matthew W., Yale University Press, 2007, .
{{DEFAULTSORT:Regrading In Seattle
Geography of Seattle
History of Seattle