Chris McCandless arrives at the Lake Mead National Recreation Area on July 6 and drives his Datsun to the south shore of the lake. It is 120 degrees Fahrenheit. He camps at the edge of Detrital Wash. It rains for a week, flooding the wash and rendering his car temporarily unusable. McCandless decides to abandon the car, bury the license plates and some of his possessions, and burn the $123 of cash he is carrying. On July 10 he hikes around the lake but suffers from heat stroke. He returns to the road.

For the next two months McCandless hitchhikes around the West, moving through Lake Tahoe, the Sierra Nevada, and the Pacific Crest Trail. He works in Northern California, where he is picked up by a woman named Jan Burres and her partner, Bob. Chris goes to Carthage, where he meets and works for Wayne Westerberg. On October 28 he goes to Needles, California, and walks overland to Arizona, where he buys a canoe and decides to paddle down the Colorado River. During this journey, he sends a postcard to Westerberg from Yuma, Arizona, thanking him for his hospitality.

McCandless makes it to Mexico by way of the Colorado River but soon gets lost in a series of canals.