What is highway 66? What does it represent? Is number 66 in itself suggestive of anything?

Highway 66 is the main migrant road stretching from the Mississippi River to Bakersfield, California. It is a road of flight for refugees from dust and poverty. The people stream out onto Highway 66, risking the breakdown of their undependable cars on the way. The is no symbolic meaning for the number, as government highways are named by the government in a way that orders them on maps for easier navigation.