Northwest Portland is in reality an entire quadrant of the city, but when most Portlanders talk about the Northwest, they are talking about a rather compact set of neighborhoods just to the north of downtown across Burnside Street, which divides north from south in Portland street parlance, and below the lofty flanks of the West Hills.
These neighborhoods are Chinatown [1] (a northern section of Old Town), the Pearl District [2], and NW 21st and 23rd Avenues [3].
There aren’t hard-and-fast boundaries between these areas, and in fact as all these areas gentrify it’s difficult to segment them one from the other.
Links:
[1] http://www.moon.com/destinations/oregon/portland/sights/northwest-portland/chinatown-and-japantown
[2] http://www.moon.com/destinations/oregon/portland/sights/northwest-portland/pearl-district
[3] http://www.moon.com/destinations/oregon/portland/sights/northwest-portland/nw-21st-and-23rd-avenues