When was the Constitution of the United States ratified?

The Constitution of the United States was ratified in 1788, and it officially took effect in 1789. The correct answer reflects this timeline as 1789 is when the Constitution was implemented after the required nine states ratified it. This significant event marked the transition from the Articles of Confederation to a new system of government that established the framework for the federal government and included the separation of powers among the branches of government.

While 1787 is the year the Constitutional Convention took place, where the Constitution was drafted, the ratification process extended into the following year. The other options represent significant years in American history but do not pertain to the ratification of the document. For instance, 1776 is notable for the Declaration of Independence, and 1791 is recognized for the ratification of the Bill of Rights, which comprises the first ten amendments to the Constitution.