The article would be better title "the not black city", as it goes on to use the African American population as the demographic for the cities 'whiteness'.
The article goes on to use Portland as "America's ultimate White City". However, looking at demographics, it is 78.6% white (http://en.wikipedia.org/wiki/Portland,_Oregon#Demographics) compared to the average of 75.0% (http://en.wikipedia.org/wiki/Demographics_of_the_United_Stat...). This isn't nearly as striking as the 6.0% vs 12.8% African American demographic in the article.