Hi Carol,

I think that your ID of Agaricus xanthodermus is quite likely. It is present in PNW gardens, has dark gills, an annulus, generally looks like the one you have, and stains yellow like the one you have. Next time you pick one for ID try to dig it out from the base rather than ripping it -- one of the essential identifying characteristics of an Amanita is that it grows from a sort of egg-like base. Google "Amanita egg" for pictures. But yeah, the gills don't indicate Amanita -- they tend to have light colored gills. You can also do spore prints to refine your identifications.

Note that I'm not 100% certain of your ID on this particular species because I haven't IDed one before in person -- I'm mostly interested in knowing edible mushrooms and those that look similar -- but the characteristics do add up. There are a couple of PNW mushroom Facebook groups (the one I am in is PNW Mushroom Foraging and Identification) and you could ask them for an ID (but they can be really hit or miss -- sometimes you get David Arora, the well-known mycologist, responding and sometimes you get a random person responding who has no clue but acts like they do, or who gets upset if someone pulls a mushroom rather than cuts it (evidence seems to suggest that either way is fine).

Nice mushroom!