Yellow Wildflower

These are growing all around the Arnold, California, area, and they are a beautiful yellow color on dark green foliage. They are very stunning, but I do not know their name. They look like some kind of iris or daffodil, or a cross between them. If any of you know what these are, please help me out. Thanks.

After some additional research, I believe this is a Great St. Johnswort.