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DAY 1: The 60-mile (97-kilometer) stretch of I-84 between Portland and Hood River is the portal to the densest concentration of waterfalls in the nation. See at least one. Wahclella Falls tumbles 80 feet (24 meters) into a moss-swaddled pool just a half mile (0.8 kilometers) from the Tanner Creek trailhead and is a delightful detour en route to Hood River. In town, pick up a kayak at Hood River Outfitters and a bagged lunch next door at the New York City Sub Shop, then paddle to one of the sand beaches on Miller Island for an idyllic picnic. Situated about a half mile from shore in the heart of the Columbia River Gorge, Miller rewards visitors with large numbers of unofficial hiking trails. Bed down later at the Hood River Hotel after a celebratory beer at the funky Sixth Street Bistro and Loft.

DAY 2: To get started on an overnight backpacking trip in the Indian Heaven Wilderness, one of Washington's most underrated, head 54 miles (87 kilometers) northwest of Hood River to the Placid Lake Trailhead. On the five-and-a-half-mile (8.8 kilometers) hike to Deer Lake, you'll wander through deep groves of fir and fields of huckleberry bushes, and along a lonely stretch of the Pacific Crest Trail. Camp by the lake—come prepared for a chilly night—and keep an ear out for late-season bugling elk.

DAY 3: The name Lemei Rock might not sound that impressive, but the view is all drama. From atop the 5,925-foot (1,806-meter) pinnacle, about two miles (3.2 kilometers) from camp, you'll be surrounded by defunct Cascades volcanoes. In a single glance, you'll catch Adams, St. Helens, and Hood rising up among snaggletooth peaks. Pack out in the afternoon and continue heading west toward the general store in the hamlet of Cougar for a taste of civilization, then to the town campground on the shores of Yale Reservoir.

DAY 4: The biking at Mount St. Helens is legendary among Portlanders and Seattlites, and no trail is more storied than Ape Canyon. One hitch: It's B.Y.O.B.—no bike rentals in these parts. The route climbs five and a half miles (8.8 kilometers) through old-growth forest and skirts the largest mudflow on the peak's south side. Highlight: at the canyon's top where you join the Loowit Trail. Coasting from the deep, primeval forest onto the surreal blast zone over the Plains of Abraham, a rocky expanse on the volcano's east flank, is like being on Mars. Hit the trails over the plains, then point your nose back down the canyon—the screaming 1,300-foot (396-meter) descent over broken volcanic pumice is a St. Helens rite of passage.

VITALS: Wahclella Falls, Columbia River Gorge National Scenic Area (+1 541 308 1700). For kayaks: Hood River Outfitters ($30 a day; www.hoodriveroutfitters.com). For hiking details: Mount Adams Ranger Station (+1 509 395 3400). For biking info: Mount St. Helens National Volcanic Monument (+1 360 274 0962). For the Cougar Campground: Pacific Corp ($15; +1 503 813 6666). Hood River Hotel ($69 a night; www.hoodriverhotel.com).