DILLINGER RIVER, APRIL 17
"Despite my best efforts, my leather ski boots got soaked by the melting snow," says Skurka, who tried to leap across some creeks and rivers. "At night everything froze solid. In the morning I had to force myself to slip my feet into the icy boots."

BULL RIVER VALLEY, DENALI NATIONAL PARK, APRIL 26
"My feet were rarely dry," Skurka says. "The usual causes were melting snow, river fords, muskeg bogs, and rain-saturated tundra. The key to maintaining the health of my feet was getting them warm and dry at least every night, and ideally once during the day too. I'd take off my shoes and socks, put them out in the sun, start a fire if I had to, and put on a clean and dry pair of socks before going to bed."

DENALI NATIONAL PARK, APRIL 27, 2010
"Skiing over this unnamed pass made me nervous," says extreme trekker Andrew Skurka. "I was worrying about an avalanche due to the warm and sunny spring weather." With 1,120 miles behind him, he still had 3,559 to go.

CHITISTONE PASS, WRANGELL-ST. ELIAS NATIONAL PARK, MAY 19
"I'd swapped out my skis for my hiking shoes on May 13, thinking that there was no longer enough snow along my route to warrant them," Skurka says. "Then I got to 5,822-foot Chitistone Pass, where it was still winter. I'd picked up my pack raft at the same time, since the rivers were becoming unfordable but floatable. As it turned out, skis would have been much more useful than the pack raft I had strapped to my pack."

COPPER RIVER, MAY 26
"The ice lingering on Miles Lake was too soft to walk on and too hard to paddle through," Skurka says. "My only option was to scoot across in my one-person inflatable pack raft." Thirty miles downstream, summer had arrived, with vegetation in full leaf and mosquitoes in full force.

CORDOVA, MAY 27
"After my parents, the United States Postal Service played the most important role in my trip logistics," says Skurka. "Food, supplies, maps, and fresh gear were all sent in Priority Mail flat-rate boxes, addressed to general delivery. I'm still not sure how a 12-pound box of food can be shipped from Massachusetts to bush-village Alaska for just $15, but I don't want to question it. Receiving new shoes, a stack of crisp maps, pounds of chocolate, and (if I was lucky) some homemade cookies from Mom was one of the most cherished experiences of the trip."

GULF OF ALASKA COAST, JUNE 8
"If this coastline were anywhere in the lower 48, there would be a highway running parallel to it and high-rise hotels overlooking it," Skurka says of the Gulf of Alaska. "Instead, the coast here remains nearly as wild as it was when Captain James Cook first sailed it in 1778, save for an occasional outpost of civilization and a preponderance of marine trash."

ALATNA RIVER VALLEY, AUGUST 19
"I paddled across this deep, slow-moving river in my small pack raft," Skurka says. "As soon as I got to the other side, I built a big sandbar fire to warm up and cook dinner." The Alatna meanders south from the Gates of the Arctic National Park.

ARRIGETCH PEAKS, GATES OF THE ARCTIC NATIONAL PARK, AUGUST 22
"My route through the Arrigetch went up and over 6,685-foot Ariel Peak, the pyramid-shaped mountain capped by an overhanging horn in the background of this photograph," Skurka says. "Surprisingly, this was the most practical way of getting over the main Arrigetch crest—the Class 3 scramble was better than the technical climbing or the precariously balanced talus found on other routes. I woke up early that morning, excited about the terrain ahead and knowing that a morning fire and coffee would be welcomed by the National Geographic crew who had joined me for this stretch."

ARRIGETCH PEAKS, AUGUST 23
"These teeter-tottering granite boulders all wanted to slide," Skurka says of a talus-covered pass in the central Brooks Range. "My friend Roman Dial had joined me for this section. We took forever descending the 700 vertical feet of precariously balanced rocks slick with lichens."