We have two species of Epipactis here in the Pacific Northwest, one a native and one a European import. Strangely, the import is more common than the native. The native is Epipactis gigantea, also known as the Stream Orchid or the Chatterbox (in reference to its moveable lip). The European import is Epipactis helleborine, the Broad-leaved Helleborine.
The native Epipactis gigantea ranges from British Columbia to Mexico and east as far as the Dakotas. It is quite rare in our area and we know of only a couple of sites in Washington. It grows in very wet areas, often at the side of lakes and streams and is sometimes very difficult to photograph for that reason. It grows up to 100 cm tall, but is usually smaller with around 20-25 flowers per spike.
Epipactis helleborine originates in Europe but has spread across much of the northern USA and southern Canada, and is some areas is considered little more than a weed. This can be as tall as 120 cm with around 50 flowers per spike. It seems to be very tolerant of different conditions, growing in full sun as well as heavy shade and in both wetter and drier locations.