When was the U.S. Constitution ratified?

The U.S. Constitution was ratified in 1788. This pivotal event marked the formal acceptance of the Constitution as the governing document of the United States after it was proposed at the Constitutional Convention in Philadelphia in 1787. Ratification required the approval of nine out of thirteen states, and by June 1788, this threshold was met. The Constitution officially took effect on March 4, 1789, after all necessary states had ratified it, but the crucial step of ratification occurred in the preceding year.

The other dates offered reflect significant but unrelated events. For instance, 1776 is primarily associated with the adoption of the Declaration of Independence, which announced the colonies' intention to separate from British rule. The year 1791 is notable for the ratification of the Bill of Rights, which is the first ten amendments to the Constitution. However, these events do not pertain to the ratification of the Constitution itself but rather to its subsequent amendments and foundational proclamations.