List of all species known to grow in Oregon and their habitats, as compiled from shroomery.org:
Conocybe cyanopus: Rarely found in cool climates of North America and Europe in May through September usualy in dense shade scattered among mosses, and in wet soil around bogs, swamps, ditches, in lawns, fields, and grassy areas. Difficult to safely identify as similar looking Conocybe species are deadly.
Panaeolus cinctulus (aka P. subbalteatus): it is the most common and widely distributed psilocybin mushroom. Found from spring to autumn alone or clustered in freshly installed lawns, straw piles, all types of compost, and dung piles in all 50 states and every country in the world. They grow in large numbers on the manure compost piles that are nearby any stable, race track or place where horses are kept.
Psilocybe azurescens: Found in autumn scattered, grouped, or clustered in woods, on earth, among leaves and twigs, and occasionally on decomposing wood -- in northwestern USA.
Psilocybe baeocystis: Found in autumn and winter, solitary, grouped, or clustered on earth, lawns, mulch, and decomposing forest wood near scattered trees especially conifers -- in western Oregon and Washington. It was once found in Maine.
Psilocybe cyanescens: Found in autumn scattered, grouped, or clustered on wood chips, among leaves and twigs, and occasionally on decomposing logs -- in northwestern USA. In California it fruits September through January and its range extends from the northern border south to Santa Cruz.
Psilocybe pelliculosa: Found September to December scattered, grouped, or clustered on humus and debris, in or near conifier forests in northwestern USA and as far south as Marin County, California.
Psilocybe semilanceata: Found among grasses, in clearings, pastures, meadows, forest edges, open conifier woodlands, and on roadsides -- but never on dung -- in New York, northern USA, British Columbia, and Europe. In the U.S., the season starts August through December (with the main season being in October and November). In Europe the season is September through November, starting earlier farther north and at lower elevations.
Psilocybe strictipes: Found in October rather clustered on soil or on decomposing wood and debris, on conifiers and some other trees in northwestern USA (especially in Oregon).
Psilocybe subaeruginascens: Found from southern California to Washington and also Japan and Java. It resembles and shares similar wood chip habitats with Psilocybe cyanescens however it fruits in warmer weather and is often found after spring rains.