On what date did the United States Bill of Rights become part of the Constitution?

The United States Bill of Rights became part of the Constitution on December 15, 1791.

The Bill of Rights consists of the first ten amendments. James Madison introduced proposed amendments in Congress after Anti-Federalists argued that the new Constitution needed explicit protections for individual liberties and limits on federal power.

Congress approved twelve proposed amendments on September 25, 1789, and sent them to the states. Article Three through Article Twelve were ratified by the required number of states on December 15, 1791. They became Amendments One through Ten.

The original proposals did not all become part of the Constitution. The first proposed article, concerning congressional apportionment, remains unratified, while the second proposed article eventually became the Twenty-seventh Amendment in 1992. The Bill of Rights protects freedoms including religion, speech, press, assembly, and due process.