That was written by Merle Haggard after he got out of prison and was living in Bakersfield, which was the promised land to Oakies fleeing the dust bowl, and is still a trucker and Country-Western music hub. But if that was their promised land, I'd sure hate to see where they came from. Farm labor conditions were brutal (Steinbeck wasn't exaggerating, nor was Dorothea Lange the photographer), and to this day, Bakersfield has the worst air quality in California, and possibly the nation. But Kern County also holds the highest peak in the lower 48, plus Sequoia National Park with the largest trees on earth, rugged canyons twice as deep as Grand Canyon, and some of the most spectacular wildflower displays on the planet.
Merle was actually more like a Hippie in certain ways than the type of character painted by that song. He got his inspiration when Johnny Cash visited San Quentin Prison.