This is primarily a western species, as can be seen in their range map:
Cardinal Meadowhawks are so intensely red that they almost seem unreal—as if they might be made of bright red plastic. Their abdomens are pure red, with no consistent black markings as in so many meadowhawks. In addition, the abdomen is noticeably flattened; that is, wider than it is high. Their eyes and face are red, and they have two white spots on the sides of the thorax. In fact, these white spots are what remain of white stripes in younger individuals. With age the stripes fade away, leaving just a spot at the base of each stripe. The white spots are often hard to see because the Cardinal Meadowhawk has a tendency to fold its wings forward when perched, hiding the sides of the thorax.
Better field marks, and ones that aren't mentioned in many field guides, are the dark red patches at the base of the wings—especially the hindwings. These patches are diagnostic for this species, and are readily seen even when the dragonfly is perched, facing away from you, and folding its wings forward.
Here's another look at the dark red (tending toward black with age) patches in the wings:
Find out more about this species, and the other common dragonfly and damselfly species of the Pacific Coast, in my new field guide: