The United States Constitution came into effect on June 21, 1788, after being ratified by nine of the thirteen states. It established the framework for the federal government and is considered the supreme law of the land. Its principles, such as separation of powers and checks and balances, remain vital to American governance. The Constitution has been amended over the years to address changing needs and societal values, most notably through the Bill of Rights, which guarantees individual liberties. Its endurance and adaptability have made it a cornerstone of democracy in the United States.