In what year was the Constitution of the United States ratified?

The Constitution of the United States was ratified in 1787, which marks a significant turning point in American history. This year is pivotal because it is when the Constitution was drafted during the Constitutional Convention in Philadelphia. Following the drafting, it was sent to the states for ratification, with the process culminating in 1788 when enough states had ratified it for it to take effect in 1789.

The other years listed are important in their own right but refer to different events in U.S. history: 1776 is the year the Declaration of Independence was adopted, announcing the colonies' break from British rule; 1791 is notable for the ratification of the Bill of Rights, the first ten amendments to the Constitution, which were added to protect individual liberties; and 1803 marks the year of the landmark Supreme Court case Marbury v. Madison, which established the principle of judicial review. Each of these events plays a crucial role in the development of U.S. governance and civil rights but do not pertain to the ratification of the Constitution itself.