For King County, again may change slightly but still good indication percentage wise. Since numbers not final, just gave percentages. Looks like Seattle might be in the running for most Democratic city as has beaten out San Francisco and Boston and likely New York City. Mind you one of the more well to do, quite educated so somewhat makes sense. Washington DC is more Democratic and Detroit probably is too (large African-American), but ranks up there.
Seattle:
Biden: 89.5%
Trump: 8%
Rest of King County
Biden: 69.1%
Trump: 27.6%
East end which was once solidly Republican is where GOP floor has fallen through. Not surprising as large tech sector, large number of well to do college educated residents.
Biden:
Affluent suburban Republicanism has collapsed (and Trump is a terrible fit for Mercer Island, Bellevue etc) and Seattle is one of the most left-wing cities in America.
That's very true, but these internal swings are very interesting. We always talk about Orange/Loudon/Gwinnett because you can see their color change on a map, but the swing in Eastside King County is even more dramatic. Iirc, this area (which could really be its own county) swung something like 50 points left since 2000, which dwarfs swings literally anywhere else on the West Coast.