What events occurred when McCandless left Bullhead City?

Mcandless goes to a place known as the "Slabs". THis is from the text:

"Jan and Bob were staying three miles outside of Niland, at a place the locals call the Slabs, an old navy air base that had been abandoned and razed, leaving a grid of empty concrete foundations scattered far and wide across the desert. Come November, as the weather turns cold across the rest of the country, some five thousand snowbirds and drifters and sundry vagabonds congregate in this otherworldly setting to live on the cheap under the sun. The Slabs functions as the seasonal capital of a teeming itinerant society-a tolerant, rubber-tired culture comprising the retired, the exiled, the destitute, the perpetually unemployed. Its constituents are men and women and children of all ages, folks on the dodge from collection agencies, relationships gone sour, the law or the IRS, Ohio winters, the middle-class grind."