In what year was the Constitution ratified?

The Constitution of the United States was ratified in 1788, making this the correct answer. The ratification process began after the Constitution was signed by delegates during the Constitutional Convention in Philadelphia in September 1787. The newly drafted Constitution then needed to be approved by nine out of the thirteen states to take effect. This process of ratification took nearly a year, culminating in June 1788 when New Hampshire became the ninth state to ratify it, thereby bringing the Constitution into effect.

The other years mentioned, such as 1783, mark important events in American history, like the Treaty of Paris which ended the Revolutionary War, while 1790 is notable for the establishment of the federal capital in Philadelphia after the Constitution took effect. However, the completion of the ratification process and the official acceptance of the Constitution as the supreme law of the land occurred in 1788.