While I was out and about this weekend, this enormous mushroom caught my eye. It was growing alongside our road, between the neighbor's mailboxes and their drive way. It was the largest mushroom I have ever seen in our area. The cap alone was easily 8 inches across and the stem was really thick. I was especially surprised to see a new mushroom growing in August. Normally our mushroom "seasons" are April and then again in October, after the rains have returned. We haven't had any significant moisture now in over a month.
I took a bunch of pictures and returned home. I then got out my Mushrooms of the Pacific Northwest book from Timber Press ( thanks Santa!). After a little searching and comparing I think I have a positive identification.
I am pretty sure this is "Agaricus augustus" - the Prince. It describes this as a fairly common mushroom that appears in the Summer, particularly in well watered areas underneath true cedars. It is also found in forests, along disturbed areas, such as trails or roads. Among its distinguishing features are its large size and the warm brown color of the cap scales. My find matches this description pretty well.