It's not over yet, but at least for now Alaska's vast Arctic wilderness will remain home to native species, not oil wells. In the constant sunlight of its summer, Bruce Stutz explores the wildlife refuge that dwarfs them all

Our plane tracks north from Alaska's southern coast, up the Copper River, then east along the Chitina, crossing high glacier-draped mountains and broad river valleys that put IMAX to shame. Spring runoff has been heavy and sudden, and the two swollen rivers twist down through the spruce forests and snowy peaks of the Chugach, Wrangell, and St. Elias ranges. As we descend to a gravel landing strip in Wrangell–St. Elias National Park, moose and buffalo hightail it from our shadow. Then the rough-hewn log cottages appear, basking in the glow of the low sun. Paul and Donna Claus call the lodge Ultima Thule, after the mythical northernmost region of the habitable world. But on this trip Ultima Thule is only a stop on the way to territory even more remote; indeed, all but uninhabited.

That night, at dinner around a long table, we discuss our plan to explore the Arctic National Wildlife Refuge, some eight hundred miles to the north. ANWR (pronounced ANN-wahr) is bordered on the north by the Arctic Ocean and on the east by Canada's Yukon Territory. On the map, we trace our route across the east–west arc of the Brooks Range, which bisects the refuge.

Paul has dressed for dinner, which means he's taken off his baseball cap and aviator shades. He has a boyish look, an impish grin, but blue eyes too cool to mistake him for a choirboy. He's a compact package with heavy-duty hands. Donna, robust and always bustling, has a round face just as rubicund as Paul's. Both have been divers, commercial fishermen, skiers, and climbers. Paul all but summited Everest. The St. Elias Wilderness is the Clauses' backyard, where their guests climb, raft, and ski, and where they live with their three children. These are Alaskan kids: homeschooled, practiced in the practical, eager for adventure. At seventeen, Elie keeps fifty sled dogs and has already won one junior Iditarod and two Yukon Quests.

Elie and Jay, their fourteen-year-old son, are also learning to fly, for this is bush pilot territory, made for light and maneuverable high-winged planes. Paul Claus's one-of-a-kind DHC-3 De Havilland Otter—a red-and-yellow, single-prop, jet-powered beauty—is the envy of his peers in Alaska, where bush pilots boast a status someplace between gunslinger and Knight Templar. An Anchorage museum is dedicated to their exploits, and Claus, a second-generation bush pilot (his father, John, at seventy, still flies), is a future hall-of-famer.

A decision is made, one in keeping with the ideals of Ultima Thule: no itineraries. Each day will be unique. Our plan is to have no plan at all but to head north into the refuge, land somewhere that looks good, camp, hike, scan for caribou herds, and move on.

The Otter, filled with gear and food, will serve as our mobile base of operations. I've packed fine-mesh overpants, a shirt, and a hood, in order to appear as much as possible like a screen door to the more than two dozen species of Arctic mosquito variously and harrowingly described in the literature as "voracious armies" or "oppressive hordes" that can "emerge explosively" and "drive an animal or human insane."