The underclass is perpetuated by economic inequality in the United States. Poor, low income neighborhoods that struggle to get by and a reliance on government welfare. Lack of economic resources leads to lack of education, and lack of education perpetuates lack of resources, and it becomes a vicious cycle. Certainly some of this underclass could be attributed to racism, but the majority I would say has to do with the way the economic and tax systems are set up to work in the United States.
According to william julius wilson, racism has created a black underclass, but this underclass is perpetuated by: