The United States has a federal democratic republic form of government. This means that the country is an indivisible union of 50 sovereign states, where people govern themselves and choose elected officials by free and secret ballot. The government derives its power from the people, and the Constitution of the United States is the supreme law of the land. The Constitution establishes three main principles on which the government is based: inherent rights, self-government, and separation of powers. The federal government is composed of three distinct branches: legislative, executive, and judicial, whose powers are vested by the U.S. Constitution in the Congress, the President, and the Federal courts, respectively. The three-branch structure is not required for state governments, but all state governments are modeled after the federal government and consist of executive, legislative, and judicial branches.