The expansive 1.3 million acres of the Andreafsky Wilderness cover only slightly more than 5 percent of the monstrously vast 20-million-acre Yukon Delta National Wildlife Refuge, America's largest unit of the National Wildlife Refuge System. Most of the delta is wetland tundra and marsh, and about one-third of it lies underwater. Here you'll find moose, foxes, beavers, martens, minks, wolves, wolverines, caribou, large populations of black and brown bears, and millions of salmon. The Andreafsky River and its East Fork, in the northern section, flow southwest along parallel paths and drain into the Yukon River. Forests of white spruce and balsam poplar grow along the riverbanks through the Wilderness. Near the headwaters the forests give way to alpine tundra, and a relatively flat, treeless delta. Fishing is excellent, and the bears know it. Both rivers are scenic, but the East Fork has more trees and runs closer to the mountains. One hundred twenty-five miles of the Andreafsky and 137 miles of the East Fork are designated National Wild and Scenic Rivers, attracting river runners and anglers. Summers are cool and gentle by Alaskan standards, with days of fog. Winters are cold, dry, and severe.