They met at the most important place, near the truck…this was the new hearth, the living center of the family.
– John Steinbeck
The Grapes of Wrath, Chapter 10. Now that the nomadic Joads are without a real home, they gather for a family meeting near the truck. Since "house was dead, and the fields were dead," the truck becomes their most important possession. Is is their new home and means of survival on the road. It sustains them and they depend upon it to take them to California.