What makes the West Coast so solid?

[Citizen Hats]

While I can't personally explain Oregon, I have some explanations for California, which is actually the most urban state by population share.  There really aren't that many people beyond the suburbs.

California is an ancestrally Republican state, which leaves it with a wide base of the sorts of affluent people who don't quite appreciate the southern-fried flair of the modern Republican Party, as in the North East.  This gives the Democrats a baseline of white support.  Following that, California's hispanic population were deeply alienated from the Republican Party in the 1990s when they joined the 'kick the Mexican's kids out of school' bandwagon. At the same time, Texas Republicans were building bridges, Californian Republicans were mercilessly setting them alight.

The State was never a home of lots of heavy industry, which leaves a fairly small post-industrial working class to resent things. 

Lastly, the state is demographically dominated by not one, but two of the largest metropolitan areas in the country.  San Francisco's particular liberalism has been linked to it's heritage as the sort of ultimate gold rush boom town, and as a place where large numbers of gay sailors put down routes during the war when they left the military, rather than return home.

[Citizen Hats]

Geography. There is a stark geographical contrast between the coastal regions and rugged desert-like interior, and this leads to a stark cultural contrast between the regions as well. The coastal region is highly desirable real estate with many wealthy individuals and powerful businesses. Nearly all citizens and businesses are ecologically conscious. The interior regions are populated by redneck bumpkins, farmers and energy/resource people who exploit the earth, exterminate animals, and carry guns. They want to be free of urban regulatory entanglements.

The clash of cultures is more stark than any electoral rhetoric, and since most people on the Left Coast live in the coastal region, the states are solidly Democratic.

If the interior turned into agricultural panhandlers whose only desire was stealing coastal money via wealth redistribution, the coast would turn red.

Have you looked at the economics of irrigation in California? They already are panhandlers

[Citizen Hats]

Have you looked at the economics of irrigation in California? They already are panhandlers

Compared to Redwood rainforest-dwellers, maybe, but not compared to coastal residents in SoCal. Despite the drought, the Santa Fe Irrigation District in Northern County, where my parents live, is consuming almost 600 gallons per capita per day.

A farmer can feed a city with that kind of water, but a family of four in San Diego can't keep their geraniums alive or their pools full with less than 2,400 gallons a day.

A lot of the areas of the central valley have never even paid back there water bonds, like the Westlands, and rely on expensive state and federal capital funding to be even remotely profitable