[1] They were introduced by James Madison to the First United States Congress in 1789 as a series of constitutional amendments, and came into effect on December 15, 1791, when they had been ratified by three-fourths of the States. Thomas Jefferson was the main proponent of the Bill of Rights.

[2] The Bill of Rights prohibits Congress from making any law respecting an establishment of religion, forbids infringement of the right to keep and bear arms, by Congress or citizens in a federal territory 

[3] and prohibits the federal government from depriving any person of life, liberty, or property, without due process of law. In federal criminal cases, it requires indictment by grand jury for any capital or "infamous crime", guarantees a speedy public trial with an impartial jury composed of members of the state or judicial district in which the crime occurred, and prohibits double jeopardy. In addition, the Bill of Rights states that "the enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people,"

[4] and reserves all powers not granted to the federal government to the citizenry or States. Most of these restrictions were later applied to the states by a series of decisions applying the due process clause of the Fourteenth Amendment, which was ratified in 1868, after the American Civil War. 

Madison proposed the Bill of Rights while ideological conflict between Federalists and anti-Federalists, dating from the 1787 Philadelphia Convention, threatened the overall ratification of the new national Constitution. It largely responded to the Constitution's influential opponents, including prominent Founding Fathers, who argued that the Constitution should not be ratified because it failed to protect the basic principles of human liberty. 

The Bill was influenced by George Mason's 1776 Virginia Declaration of Rights, the 1689 English Bill of Rights, works of the Age of Enlightenment pertaining to natural rights, and earlier English political documents such as Magna Carta (1215). Two additional articles were proposed to the States; only the final ten articles were ratified quickly and correspond to the First through Tenth Amendments to the Constitution. 

The first Article, dealing with the number and apportionment of U.S. Representatives, never became part of the Constitution. The second Article, limiting the ability of Congress to increase the salaries of its members, was ratified two centuries later as the 27th Amendment. Though they are incorporated into the document known as the "Bill of Rights", neither article establishes a right as that term is used today. For that reason, and also because the term had been applied to the first ten amendments long before the 27th Amendment was ratified, the term "Bill of Rights" in modern U.S. usage means only the ten amendments ratified in 1791. 

The Bill of Rights plays a central role in American law and government, and remains a fundamental symbol of the freedoms and culture of the nation. One of the original fourteen copies of the Bill of Rights is on public display at the National Archives in Washington, D.C.