A brief history of Lake Washington
based on the results of my research on the Black River & Lake Washington

Seattle is unusual, perhaps unique, in that it is a major city built during and after the industrial revolution. (I have heard stated, and i don't know how true this is, that Seattle is the youngest city of it's size, and/or the largest city of it's age, in the world.) When Europeans arrived here they did so with the stated intention of building a metropolis -- this is very different than the history of other US cities such as Chicago or Boston or Philadelphia, which just grew up haphazardly from small settlements. (But NOT Washington, DC or mid-town Manhattan, which are essentially the same age as Seattle) The effect of this is obvious in many ways in Seattle, such as in the rigid street grid and highly structured, albeit bizarre, address system. But perhaps the most dramatic evidence of this is the way that the land itself was altered.

Seattle is built on a narrow isthmus ranging from 2.3 miles to 7.7 miles across. In the middle of the isthmus are two small lake basins surrounded by steep glacially carved hills.

The Lake Union basin is in the central portion of the isthmus. Green Lake, 4300 feet by 2200 feet and reaching a depth of 24 feet, is in the northern portion of the isthmus; Green Lake was formed by a huge chunk of glacier that broke off and just sat in the middle of the land melting.

The Seattle Isthmus is bounded on the west side by salt water Puget Sound, with Elliot Bay, 2 by 4 miles and 620 feet deep jutting significantly into the city. The eastern boundary of this isthmus is a very large fresh water lake.

In the early part of this century a great deal of engineering was done on the land in and around downtown Seattle. Portions of many of Seattle's hills were carved down and sluiced into the bay. The Dearborn Street/Jackson Street area, near where I-90 is now, was heavily re-graded as was the area around Madison Street downtown. Most notably, of course, was Denny hill, whose 283 foot peak was between 3rd & 4th Avenues between Blanchard & Lenora Streets in Belltown; the entire area is now a flat 100 feet above sea level. The neighborhood is now more often know as "The Regrade", although this re-grading actually went back to the north east most of the way to Lake Union. The massive regrading stopped, in large part because the newly invented automobiles were able to climb the hills far easier than a horse and carriage -- Although there was even a suggestion (in the 40s) by the then Mayor of Seattle to dig out and flatten Queen Anne Hill and use the dirt to fill in Lake Union to build another neighborhood!!!!

But the most obvious, and extreme changes were made to the waterways -- the lakes, rivers, harbors and tideflats surrounding Seattle. Rivers were created and others removed, tideflats were filled in and harbors dug, islands were created, and of course, the Lakes that so define what Seattle is were significantly altered. All of this was done for flood control, national (and international) recognition, to assert sovereignty, create shipping access and therefore stimulate economic growth. It was seen as a way to build a major metropolis -- in my opinion the major reason it was done, was simply because they could. I don't think anyone thought about the effects.

Of the waterways, the two most notable are the two major Seattle Lakes. Smaller, and more westerly is Meman Hartschu, named Lake Union by the white settlers in the hopes that it would one day connect Lake Washington with the Puget Sound. Several tourist outfits in town incorrectly suggest that the name was chosen because David Denny, the person who named the lake at a now famous Fourth of July picnic, was a "staunch Unionist". This is inaccurate.

Lake Union averages 54 feet deep and never reaches more than 64 feet deep. It is approximately 7 miles around with 688 acres or 1.08 square miles of surface area. (7600 feet x 2200 feet). It was considerably larger before the city was built, due to a great deal of fill for development on the shores during the last 80 years -- especially on it's western shore, the shoreline was originally Queen Anne Hill!. According to one source, the surface of Lake Union was originally at about 25.5 feet above Salmon Bay's mean low water mark. (The extreme tidal range at Seattle is 19 feet!!) and about 10 feet below the level of the larger Lake Washington. There were swamps and marshes along the east side of the lake at the location of today's Fairview Ave and at the southwest corner.

Once a gorgeous basin surrounded by forested hills with many tiny streams flowing into the salmon filled lake, Lake Union is now a decidedly urban lake. Surrounded on all sides by central Seattle, with dense neighborhoods covering the slopes on every side, it is still a shipbuilding center and fishing base. Many of the other larger industries of past decades have moved away and much of the lake is turning into upscale residential, with over four hundred of the homes actually floating on the surface of the lake.

I picture this lake as a gorgeous basin with bears ambling along eating blueberries at the edge of the giant trees. For centuries there was a low point full of blue berry bushes near the south end of Lake Union. The Duwamish people called it 'the place where the bears are' and like the bears it was a meeting and celebration place. Now on that spot is Seattle Center and the Space Needle, still the place where we meet and have our celebrations.

Lake Washington, Lake Duwamps to the Natives, is 23 miles long, north to south, 0.75 to 3.5 miles wide, averages 1.5 miles wide and contains 762 billion gallons (3.66 billion cubic yards) of water. The lake has 58 miles of shoreline, excluding islands and a maximum, and fairly consistent, depth of over 230 feet. It is so deep that normal highway bridges were impossible, so they built pontoon bridges, floating concrete, to span the lake! There is one major island in the lake, in the south part of the lake, Mercer Island -- 4152 acres, an exclusive suburb, connected by the floating bridge. There is one minor island, Foster/Marsh Island, 47 acres, in Union Bay.

There is a second very large, long lake in this drainage called Lake Sammamish. It is about 10 miles east of Lake Washington, separated by a high ridge and plateau, and drains through a small river into the northern tip of Lake Washington. At the other end of Lake Washington, the Cedar River flows down the Cascade Mountains, south and east of the city, into Lake Washington, as does the Green River. Where they join, the new river is the Duwamish, it opens in to the Port of Seattle harbor and then into Elliot Bay.

Lake Washington is the largest lake west of the Cascade mountain range and the second largest natural lake in the State of Washington (after only Lake Chelan in the Central Washington mountains). The water temperature at the surface ranges from 42F in the winter up to 70F in the summer, although deep down it is a consistent 42F. Before the digging of the Lake Washington Ship Canal and the elimination of the Black River as a drainage, Lake Washington, and the entire watershed, flooded generously every spring.

The shores of Lake Washington were covered with enormous, ancient trees 100 years ago, all of which have long been removed. But there are still 200 foot high trees on the bottom of the lake in two places, the west shoreline of Mercer Island and the eastern shore of the lake north of Juanita. This is due to a major earthquake 1000 years ago that caused large sections of forest to slide, intact, into the lake. The forests are marked on maritime maps and several years ago the local boating agencies cut the tops of them off to prevent boats from getting tangled in the trees tops.

There is a great deal of confusion as to the original surface level of Lake Washington. I've found reference to quite a few different levels, both present day levels and pre-canal levels. The most accurate i can find is the daily US Army Corps of Engineers lake levels taken at Kenmore (Northernmost end of the lake) which indicate a wintertime level of a couple of inches above 20 feet above sea level (mean low tide) during the winter and almost 22 feet above sea level in the summer. Some of the other figures i dug up include a current level of 25.5 in the summer. Figures for the original elevation of Lake Washington vary widely, 33, 34.3, 35, 37 among them. I suspect that much of this confusion is due to the fact that the lake was not very stable. Due to the dams, canals and locks, the level is very stable today.

On July 19, 1917 the last of the hill between Lake Union and Lake Washington, two entirely different watersheds, was removed -- from July 19 until October 21 the larger lake drained into Lake Union and on into the newly connected Salmon Bay and raising the formerly salt water bay's water level almost 20 feet. Lake Washington's surface level was lowered 8.8 feet.

There is quite a bit confusion as to exactly how much Lake Washington was lowered; this is probably, at least partially, due to the fact that the lake is now a very stable level, but before the engineering, it fluctuated greatly, with radically different levels in the summer and winter and flooding often.

To create what is today know as the Lake Washington Ship Canal two canals were dug. The first, a 2000 foot long channel about 100 feet wide, dug through the hill that, since the last glacial period, had separated the Duwamish river watershed and the Lake Union Basin. This canal, through a neighborhood now called Montlake ran from the steep shore of Union Bay in the western portion of Lake Washington to Portage Bay, part of Lake Union. The second, longer, canal (about 3500 feet long and about 200 feet wide) was dug starting at the eastern edge of Lake Union near the small sawmill town of Fremont and running along an existing stream to the waterfall that fell 20 some feet into the salt water and mud, of Salmon Bay. The Fremont Opera house was removed in order to dig the canal directly through its' site.

At the Western end of Salmon Bay, at the tight point between Salmon and Shilshole bays, just south and west of downtown Ballard -- a small Scandinavian fishing town -- a dam and two locks were built. The larger of these locks is the second largest lock in the world, after only the large lock in Panama. The first boat sailed through The Ballard Locks on February 7, 1916. The gates at the locks first closed July 12, 1916. Salmon Bay, originally a shallow salt water inlet, mostly mud at low tide, was now filled with fresh water and raised to, 25.5 above mean low tide, the level of Lake Union, to which it is now connected by the Fremont Cut.

The full length of the Lake Washington Ship Canal, from the Ballard Locks to Windermere Point, including Salmon Bay, The Fremont Cut, the northern portion of Lake Union, Portage Bay, The Montlake Cut and Union Bay, is approximately 8 miles.

There are huge gates underwater that rise up in front of the locks to prevent salt water from back flowing into the, now fresh water and therefore mis-named, Salmon Bay.

Currently the level of the lake -- that is Lake Washington, Lake Union, the two canals and Salmon Bay, they are all one body of water now -- is controlled by the dam at the Ballard Locks. Between February and April they raise the lake 18 inches, in the late fall they lower it again. This allows the Corps of Engineers enough water to operate the locks during the heavy usage in the summer and also allows space in the lakes for the winter rain and spring runoff without flooding problems. When they vary the level, they cannot change it by more than one quarter of an inch per day because of the several hundred floating homes (which have sewer connections) and the floating highway bridges, which cannot take more than 1 inch variation per day.

Several other places were suggested as places for a canal connecting Lake Washington to the Sound. The south end of Lake Union is close enough to downtown, and therefore Elliot Bay, that there was much talk about digging a canal through the Denny Hill (now Regrade) area. Also the Dearborn Street cut -- a cleavage in Beacon hill where I-90 now runs under the 12th Ave S bridge, originated as an early attempt at a canal.

Looking around the lake there are many places where the recent (80 years ago) lowering is obvious. Many of the front yards of the exclusive mansions that surround the lake have a gentle slope coming up from the lake, which abruptly changes to rocky and steep at about 11 feet above the surface of the lake. A major Seattle City park is on the Bailey Peninsula, which was an island before the lake was lowered. Juanita Bay is almost gone, the land developed into a shopping district.

Union Bay is only a fraction of the size it once was, and the University of Washington is built on much of the area it used to occupy. During the 1909 Worlds Fair row boats were launched from what is now the intersection of Pacific and Montlake Blvd. The parking lots and stadium are now where the lake was then.

Union Bay itself is only about 2 feet deep, creating a challenge for ships that veer out of the dredged shipping lanes. (I have actually seen a large fishing ship get stuck in the bay while i was kayaking!)

But most of all lowering Lake Washington had a profound effect on three rivers at two extreme ends of the lake. By simply lowering the lake, the Sammamish Slough, a very slow moving, wide ranging, swampy wetland flowing east southeastward from Lake Sammamish into the northernmost point of Lake Washington was turned into an actual river, now easily navigable, with a far more significant current. It was later dredged to create an even more distinct river. At one time hydro races were run on the Sammamish Slough but it was ended because it was so dangerous.

Lake Washington's shoreline receded several hundred yards westward down the Slough and the lake no longer backed far up the channel of the Slough during flood season. Draining this wetland opened up a great deal of farmland between the two large lakes. In addition, another major wetland, the Mercer Slough in Bellevue was significantly altered by lowering the lake. It was also dredged at some point.

At the south end of Lake Washington the lake had drained into the Black River. The Black River was short, steep & rapid; it had to fall over 32 feet in it's 4 miles. It flowed into The Duwamish river just north the current site of S 143rd St at Fort Dent County Park. Lowering Lake Washington left the river dry, even in the flood season as the dam at the locks now controlled the lake level. The riverbed was filled in and there is now an airport, and a city street (Renton's SW 7th Street) in it's place. There is a small creek in a very deep riverbed flowing into the Duwamish today at the point where these rivers once met which you can see very clearly on a southbound Amtrak Train or on the bike trail out of Fort Dent Park.

The one photo i've seen of the Black River does not show a raging torrent, but rather a placid river, nevertheless, it is clear that it was a fast moving, turbulent river. Although it is clear that logs were floated down this river, it has been hard finding information on weather the Black River was actually navigable. Some accounts claim it was not at all, but the Seattle Times, on 12/20/90 said, "Lake Washington through the Black & Duwamish Rivers had a navigable connection with Puget Sound with sufficient capacity for the transfer of floating logs." Judging from the steep drop, i would assume that logs could be floated down it, but that boats could not make their way up it, at least not easily.

The Cedar River, which rises 3500 feet up in the Cascades near Stampede Pass, originally flowed into the Black River at a bend less than a mile south of the southern bank of the lake. Together they fed water OUT OF the lake.

During spring runoff, the high flow in the Cedar river would overwhelm the Black River and the portion of the channel of the Black River between the Cedar River and Lake Washington, which currently lies beneath Renton International Airport, would reverse directions, dumping much of the melted snow from the Cascades into Lake Washington, causing the lake level to rise significantly. When the Lake Washington Ship Canal was built, and the Black River removed, the Cedar river was diverted from the Duwamish River watershed to flow into Lake Washington to supply water for the locks. This also served to eliminate the spring flooding of the lake. The current channel of the Cedar river from the Lake, through the Boeing factory and out to I-405 and the Cedar river park is actually a canal.

Much of this change has been not only forgotten by common knowledge, but by history as well. Very little information is written down about the entire process and much of what is available is conflicting.

bodies of water
  • Elliot Bay
  • Puget Sound
  • Lake Union
  • Lake Washington
  • Lake Sammamish
  • Sammamish River
  • Black River
  • Cedar River
  • Green Lake
  • Genesee Slough
  • Mercer Slough

    ASCEP       27/08        p1231  American Society Civil Engineers Pro
    PI          01/07/22                 (dams)
    PI          01/07/25         (dams)
    PI          03/10/16         (plans)
    PI          04/09/23                 (islands) 
    PI          04/11/04      p7   (Black River)
    PI          06/03/18   
    PI          71/05/30      pNWT 8&9
    PI          80/04/27      pNW3-4  
    PI          82/08/08      pPE5
    PI          96/01/09      p3
    PI          99/01/31        (dams)
    Sea Chest   74/06         p133    [#7-4]  
    Sea Chest   75/06                 [#8-4] 
    Sea Chest   75/09         p27-37  [#9-1]  
    ST          04/09/23                 (islands)
    ST          62/05/17   
    ST          62/08/01   
    ST          69/05/17
    ST          74/04/13      pA13  (Black River)  
    ST          74/04/15      pA13
    ST          90/12/20   
    ST m        69/07/20   
    ST pm       85/12/01   
    Weekly      85/10/16      p33-38      (Black River) 
    Weekly      85/10/16      p47-49      (Black River) 
    ST          85/08/04  
    WA State Division of Water Resources. Lakes of Washington, v.1 p166. v2.p99.
    Seattle Now & Then vol. I
    Seattle Now & Then vol. II
    Seattle Now & Then vol. III
    misc Seattle times 92 - 99


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