Many flowers have more than one common name, however this one has more than usual: pacific trillium, trinity flower, western trillium, western wake robin, wakerobin, western white trillium, white trillium.

western white trillium (trillium Ovatum)
The white trillium bears distinctive 3-petaled, white flowers in spring above its dark-green leaves.

western white trillium (trillium Ovatum)

white petal of the western white trillium (trillium Ovatum)

pollen covered anthers (trillium Ovatum)
Below - a cut away view of a western white trillium flower (trillium Ovatum) showing the long stem, subterranean bulb and roots.

cut away view of a western white trillium (trillium Ovatum)