James Madison originally proposed 12 amendments for the United States Bill of Rights in 1789.
Madison introduced the proposals in the First Congress on June 8, 1789, drawing on state declarations of rights and suggestions from the ratifying conventions. Congress approved 12 articles and sent them to the states. The first two proposals did not receive approval from enough states at that time.
The third proposed article became the First Amendment, so 10 of the original 12 amendments were ratified on December 15, 1791. Those 10 amendments protect freedoms such as speech, religion, press, assembly, and due process, while also addressing searches, trials, punishment, and the relationship between federal and state powers.
The original first proposal concerned the size of the House of Representatives, and the second concerned congressional pay. The congressional-pay proposal was eventually ratified in 1992 as the 27th Amendment. This is why the Bill of Rights contains 10 amendments even though Madison initially proposed 12.