Portland isn't a big city but it is a city. An urb, not a suburb. Portland actually has suburbs of its own. It has so many suburbs that they're ranked by someone who does that kind of thing (not that I vouch for the rankings):
Aside from a few blocks north of downtown on the west side of the Willamette River, Portland is entirely suburban, by my definition at least. Single family houses dominate outside of that small urban core.
Outside of Portland you could say there are suburbs, but many of them are just towns themselves that blend into Portland as the area has grown. E.g. Oregon City, which is older than Portland but might now be considered a suburb.
Outside of Portland you could say there are suburbs, but many of them are just towns themselves that blend into Portland as the area has grown. E.g. Oregon City, which is older than Portland but might now be considered a suburb.