If your impression of Oregon as a quirky island of tolerance is formed by its blue-state status and its history of progressive ballot measures (or by watching Portlandia), you should check out a fascinating history long-read by Matt Novak, writing for Gizmodo. Novak goes into great detail about Oregon's mostly-swept-under-the-rug racist past.
For starters, Oregon is the only state that explicitly enshrined outright racial exclusion into its state constitution at its founding, forbidding any black residents from living there. Novak details not just decades of Jim Crow-style segregation in Portland businesses, but also the mostly-forgotten Vanport flood, which wiped out a mostly-black section of Portland in 1948, and, maybe most shockingly, the KKK's infiltration into the state's corridors of power in the 1920s. If you've ever wondered why Portland is the nation's whitest major city, it's not merely a demographic accident.
Oregon has changed since the 1920s, but not as much as you might think. In 2002, a ballot measure passed which removed the language of racial exclusion from the constitution, and other racial references as well. You might imagine this would be a slam-dunk, nearly unanimous vote - but 29% voted against it, in a familiar geographic pattern as seen in the map above. One county passed it with only 53%. (This should be embarrassing enough, but Measure 14 actually did better than last year's equal rights amendment, Measure 89, which did not pass in a dozen counties.)
It's tempting to think the county-level pattern seen in Oregon's election results is the result of migration to Oregon's larger cities from all over the country, leaving more rural counties as representatives of an earlier incarnation of Oregon political culture. Census data show us that's not really the case, however. There's plenty of people born outside of Oregon living in rural areas as well - they're just not liberal.
It's easy to forget the extent of political diversity within states in a winner-take-all electoral system. And it's easier to leave history in the dustbin when it conflicts with the story we want to tell ourselves about our country and our communities. But history lives on and shapes our current society and its politics, whether we acknowledge it or not.
See also Mark Sumner's post on the subject.