Except for the Monarch, which is rare in thes parts of the NW, these butterflies can be seen in northern Oregon.
Western Tiger Swallowtail
Cabbage White Butterfly
Common Wood Nymph
Creating a Butterfly Garden in northern Oregon will increase the odds of seeing them. To understand what a habitat requires, check out my free online course.
Here are some general host plants for the area.
Stinging Nettle for Red Admirable, Satyr Anglewing, Milbert's Tortoiseshell
Mallow/Hollyhock for Gray Hairstreak, West Coast Lady, Painted Lady
Thistle for Painted Lady, Mylitta Crescent
White Clover for Clouded Sulphur
Cabbage/Broccoli/Kale for Cabbage White
Lupine for Boisdval's Blue
Violets for Zerene Fritillary, Great Spangled Fritillary, Hydaspe Fritillary, Western Meadow Fritillary and Pacific Fritillary
Pearly Everlasting for Painted Lady
"Wild Lilac"/Ceanothus, Buckbrush for California Tortoiseshell
Ocean Spray for Spring Azure, Brown Elfin, Lorquin's Admiral, Pale Swallowtail
Pacific Rhododendron for Gray Hairstreak, Brown Elfin
Bleeding Heart for Clodius Parnassian
Vetch for Orange Sulphur
Parsley, Dill, Fennel, Queen Anne's Lace for Anise Swallowtail
Willows for Green Comma, Mourning Cloak, Western Tiger Swallowtail, Lorquin's Admiral