Looking for,
Here is the part of the Oregon Encyclopedia you ignored:
Black Exclusion Laws in Oregon-
Opening sentence: 
"Oregon's racial makeup has been shaped by three black exclusion laws that were in place during much of the region's early history. These laws, all later rescinded, largely succeeded in their aim of discouraging free blacks from settling in Oregon early on, ensuring that Oregon would develop as primarily white".

At the conclusion  of this OE piece the author notes this constitutional clause and other laws were effective  in keeping out blacks-- there were just 128 African-Americans  in Oregon 
 in 1860.  [this was 0.24% of the total Oregon population; in 1940, strangely, it was still  0.24%!]  

Frankly, I'm at a complete loss as to why you are so determined to contradict our historians,  the NAACP at  the Mims etc. on this.  As the old cliche goes, we are all entitled to our own  opinions but not our own facts.