Lake Washington is the largest lake in King County and the second largest natural lake in the state of Washington. Seattle is found on the Western shore of the lake, Bellevue on the eastern, Kenmore on the Northern, and Renton on the south. Mercer Island sits just off of the western shore, in the southern half of the lake, which you'll barely get to see if you take Interstate 90 from Seattle to Bellevue.
The lake is fed by the Sammamish River at its north end and the Cedar River at its south. However, when we talk about "rivers", don't expect the grandeur of the Mississippi or Alleghany. These are smaller rivers, akin to creeks to those of us imagining the Thames or the Danube when we hear the word 'river'.
Lake Washington is a deep, narrow, glacial trough, created by the Vashon glacier as it receded from the area, roughly 12,000 years or so ago. The lake is 20.6 feet above mean lower low tide in Puget Sound, to which it is connected via Lake Union, the Lake Washington ship canal, and the Chittenden Locks. The canal is the only discharge from Lake Washington via the locks and dam at the western end. The development of the canals, dam, and locks resulted in the lowering of the lake 9 feet to its present level
Lake Washington was named by Thomas Mercer in 1854, when he suggested it be named after George Washington, as the new Washington Territory had been named the year before.
Other names for Lake Washington have included the Duwamish/Lushootseed name HAH-choo or Xachu ,(translating into "great-amount-of-water"), as well as Lake Geneva, Lake Duwamish, and in Chinook (Chinook being the intertribal trading language), it was called "Hyas Chuck," which means "Big Lake."