iNaturalist has “Places” either defined by data from existing places in Yahoo maps, or defined by users who upload KML files. KML files are polygons and can be easily created in Google Earth. It seems Soos Creek Park didn’t have an existing defined “Place” because county level parks don’t seem to be defined in Yahoo.
In the Layers, I turned on the Parks and Recreation Layer under More.
I figured out how to add places to iNaturalist, and added an actual polygon for its area. I used Google Earth’s layers to overlay a polygon on the park boundaries. I saved that as a .kml file, which I uploaded to iNat. The new “Place” was then automatically populated with any previous observations made inside that area. There’s now a Soos Creek Park, WA, US and below is the widget to prove it.