Northern North America, ranging south to California, New Mexico and Georgia in higher mountains.
Northern and high mountain woodlands, often associated with broken terrain and near streams.
One generation, with adults overwintering and emerging to lay eggs in spring. The new generation matures in summer to autumn, and overwinters.
Larvae will feed on a wider range of hosts than most other Polygonia species. Most favored seem to be Willows (Salix sp.) and Currants & Gooseberries (Ribes sp.). Other plants recorded include Nettles (Urtica sp.), Hops (Humulus sp.), Alder (Alnus sp.), Birch (Betula sp.), Elm (Ulmus sp.), perhaps most odd - Azalea (Rhododendron sp.), and likely others.
Some authors split this into several distinct species based on differences mostly in the color of the underside and where they are found. Generally these are considered as regional variants or subspecies by most authors. You may see names like P. hylas (gray - Rockies), P. rusticus (brown - west), or some other.
On the opposite extreme, some authors have noticed that these are extremely closely similar to the Eurasian species Polygonia c-album (their "Comma"). It is often not possible to tell, just by looking at a specimen, which continent it came from. In fact, they are so close that there is doubt if they are different species, and molecular evidence supports this close connection. In this scenario one wide-ranging species of this type is found all around the boreal regions of the northern hemisphere, and ours in North America would be called a subspecies of P. c-album, because that is the older name.
P. faunus is the only North American species of Polygonia that is this closely similar to another from Eurasia [though some specimens from mid-Eurasia, labeled as P. c-album, look suspiciously like P. comma!].
One distinction of North American populations is that they seem to occur only in cooler regions and produce only one generation per year, and there is no seasonal dimorphism (see Polygonia comma, interrogationis & progne). The Eurasian P. c-album does occur in some milder regions where it produces more than one generation and does have distinct seasonal forms.