The Constitution of the United States created the basic framework for a national government. Its writers believed in the rule of law, which is the idea that the law is over everything, including all individuals and the government itself.
The framers wanted to ensure that no part of government would be too powerful. They knew that power is something many people want, and that given the chance, one part of government, or one person, might try to take over and run things.
Because of this, the framers carefully divided powers between the national, or federal, government and the states. Before the Constitution was written, the states had a lot more power. The Constitution made the states give up some of their powers to the federal government.
Federalism is the sharing of power between federal and state governments. It is one of the unique features of the United States government. The states may deal with their own needs in their own ways. However, the states also act together to deal with matters that affect all Americans.