I have yet to visit these amazing places, so you'll have to research places to go. Hurricane Ridge in particular is a well-known location to see some unique butterflies, such as Oeneis chryxus valerata (subspecies of Chryxus Arctic endemic to the Olympic Mountains), Hesperia comma hulbirti (ssp. of Common Branded Skipper endemic to the Olympic Mountains), and Parnassius clodius olympiannus (ssp. of Clodius Parnassian endemic to the Olympics and Vancouver Island). Keep in mind that it is illegal to collect butterflies at any locations within the Olympic National Park, including Hurricane Ridge, so come armed with your camera and some macro lenses! If you do want to collect, you'll need to find similar habitat within the Olympic National Forest directly east of the Park.
Sinlahekin Wildlife Area
13,780 acres of diverse habitats and wildlife, home to nearly 90 species of butterflies, over 560 plant species (9 rare and 1 threatened), and 215 bird species. Northwest of Omak, west of Tonasket, between Loomis and Conconully. I visit this area nearly every year and am writing a guide to the butterflies found there. Use the Search bar in my blog to find past posts and photos of the Sinlahekin.
These are on the Okanogan/Whatcom county line. Slate Peak is the highest point you can drive to in the state. The peak and the surrounding meadows and talus slopes are home to many butterflies and is one of the only places in the state where you can see Astarte Fritillaries (Boloria astarte), Lustrous Coppers (Lycaena cupreus), and Melissa Arctics (Oeneis melissa).
This is a very popular place for a variety of recreation. It is easy to find Reecer Creek Road out of Ellensburg, simply follow it north all the way to the foothills, where it narrows to a one-lane forest road (NF-35) but remains paved all the way to the top. If you continue on the gravel road approximately 3 miles, you'll come to a large 4-way intersection. Turn left to go to Lion Rock (dead end), or straight to drive across Table Mountain and access several other areas (can eventually connect with Highway 97 near Blewett Pass), or right to explore a few areas along the ridge (I think this dead ends or becomes undrivable). In season, there are many options for butterflies throughout this area. For plant enthusiasts, here is a list of plants from a Washington Native Plants survey.
There are several options in this area. To get you started, take Umtanum Road (sometimes spelled Umptanum) southwest out of Ellensburg, then either turn right onto Manastash Road and follow it west to various forest roads on Manastash Ridge, or continue on Umtanum south to Shushuskin Canyon (vicinity of Umtanum Falls trail) and follow the gravel road up the ridge to various other forest roads. If you are feeling really adventurous and have a high-clearance vehicle, take Durr Road (an old wagon route) off Umtanum and follow it south across the sagebrush-covered ridges where you'll find amazing views and lots of butterflies from May through July, before dropping down into the Wenas Valley and coming out near Naches.
Great place to view birds year-round, and particularly in the winter when many ducks, geese, swans, and Sandhill Cranes pass through during migration or stay during the winter.
Mt. St. Helens National Volcanic Monument
Popular tourist destination in the summer, most of the roads close during the winter because of snow. I enjoy being near enough to visit at different times of the year to see the changing seasons. Also has several good hiking trails. Butterfly collecting is not allowed within the Monument, but the abundance of wildflowers host checkerspots, blues and other butterflies throughout the summer, providing plenty of opportunities for close-up photography.
The full hiking trail is 11 miles round trip but the first third is really all you need to do if you want to spend a whole day reveling in various habitat filled with butterflies. The first portion is a steep climb through forest, but once it starts leveling out, you'll quickly reach several small clearings with butterflies before arriving at the huge grass-and-flower-covered hill known as Grassy Knoll. The website mentions a rough road on the way up - it really is one of the better forest roads I've traveled on as far as being very level and hard-packed dirt, but is dotted with potholes in several stretches. I have no problem navigating around most of them with my Subaru and usually make the drive from Carson to the trailhead in just under an hour.
Klickitat River Canyon
You'll need to study some maps to find pockets of public land in this area, but it is well worth the effort. The area dries out quickly in late spring, so the best time for butterflies is April through June. Some good places to start are these:
Klickitat Trail (starting in Lyle)
Old Haul Road - Columbia Land Trust property acquired from Hancock Timber Company, provides a great paved road along the river for walking and biking (closed to vehicles). Note: it is usually closed each year in late July or August due to fire danger.
Columbia River Gorge National Scenic Area
Hiking trails for all levels of expertise, sweeping views of the river, gorgeous waterfalls and wildflowers. Places to visit on both sides of the river (Washington and Oregon), but most of the waterfalls are on the Oregon side. Plan to visit in late February and March for the most spectacular wildflower displays, through late May at the higher slopes of the Gorge. Many opportunities for butterfly photography and collecting (outside of parks).
Pacific Coast Scenic Byway
No better way to explore the Oregon Coast than to drive along Highway 101. I haven't been south of Florence yet, but my favorite spot on the north half of the coast is the area around Netarts Bay and Cape Meares, with the Depoe Bay area running a close second.
Baskett Slough Wildlife Refuge
Located off highway 22 approximately 10 miles west of Salem, OR. Great place to view migrating and overwintering waterfowl. Seasonal walking trails, and home to a population of the federally endangered Fender's blue butterfly (Icaricia icarioides fenderi).
Sheldon-Hart Mountain Wildlife Refuge Complex
Located in the southeastern-most corner of Oregon, and across the border into Nevada, this two-part wildlife refuge may be remote, but is an amazing place to visit. I spent one week there as part of a frog research group, and although I didn't have much spare time to seek out other wildlife, I saw numerous antelope, wild horses and burros, deer, several hawk and owl species, golden eagles and other birds, as well as a few butterflies.