DC,

What opportunity and ability would free blacks have to travel to Oregon before and immediately after 1859?  How many US Citizens/free blacks in the east would even be aware of Oregon's Exclusion clause in 1859?  How many free blacks reached Oregon to be turned away?  Is there the possibility the Exclusion clause was more about avoiding the sectional strife facing the nation over slavery than about keeping blacks out of Oregon?  It sure doesn't seem to have worked, blacks still came and stayed, not many, but not many white people came either.  Oregon's population didn't even reach a million until about 1940 and two million in 1970.

I'm sure you'll want to bring up Oregon's flirtation with the KKK but what from what I have read, once Oregonian's realized that the KKK was not about post WWI patriotism and about racism, they were among the first to give the Klan the boot and it disappeared long ago.  Are there racists in Oregon, of course and I would bet some aren't white.