US 66 also played a large role during the Dust Bowl era of the Great Depression. Refugees seeking a better life from drought and impoverished areas of the Great Plains states, often referred to as "Okies" (which started an insulting term used by long time California residents), extensively used US 66 as a means of escaping the heavily affected areas, looking for a better life in California. Western Arizona in particular provided a great obstacle for refugees traveling down US 66 to California: they would often have trouble crossing the Black Mountains on US 66 over Sitgreaves Pass. Many of their trucks would end up wrecked at the bottom of the mountain slopes next to the highway due to failed axle bearings. Refugee drivers were among the earliest US 66 travelers to hire locals to drive their often overloaded vehicles over the pass for them. The grades on this US 66 would sometimes pose a large enough challenge to these vehicles that driving the trucks in reverse over the pass was often necessary.