When the United States was founded, the Framers of the Constitution introduced the idea of federalism. Federalism is a system where the power is shared by the federal (national) government and state governments.
The Founders of the nation saw a strong federal government as a way to unify the nation and keep it strong. On the other hand, they wanted the states to have powers in order to keep the federal government from getting too powerful.
The Constitution outlines how the power is divided between the federal government and the state governments. The federal government has specific powers allotted to it. These are called delegated powers or enumerated powers.