The U.S. Constitution, which was ratified in 1788, created the basic framework for the federal government. To prevent any individual or group from acquiring too much power and thereby threatening the people's basic liberties, the Constitution separated the government into three branches:

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The video below discusses the three branches of government in the United States and the system of checks and balances incorporated into the U.S. Constitution to ensure one branch does not become more powerful than another:
Video source: Lincoln Learning Solutions.