Hi. I’m pretty sure you are dealing with bigleaf avens or large-leaved avens (Geum macrophyllum). This page from Oregon Flora (from Oregon State U.) has some nice close-up photos, and you can see that the leaves, flower, and seed head are all a good match. This page from the US Forest Service provides some additional information as well as a distribution map. Whether or not it is a weed depends on your perspective. It is a native plant, so it acts as a host plant for some caterpillars and wasn’t inadvertently brought to Oregon from elsewhere. Additionally, the native peoples of the Pacific Northwest used it for various purposes, as noted on this page from Central Coast Biodiversity. That being said, the plant can spread vigorously (at least under the right conditions), which can be a weedy characteristic, and it doesn’t appear to be a plant that is commonly grown in home landscapes. That may indicate that it is too much work to keep from taking over or simply that it doesn’t have sought-after ornamental characteristics. If you decide you want to get rid of it, you will need to ensure that you dig out the rhizomes (underground stems), which may account for it sprouting up again.