The United States Constitution articulates the structure and powers of the federal government and serves as the supreme law of the land. It was the first permanent constitution and is the oldest still in force. It originally consisted of seven articles. The first three articles articulate the doctrine of the separation of powers of the government into three branches: legislative, executive, and judicial. Articles four through six embody the concepts of federalism, describing the rights and responsibilities of state governments and their relationship to the federal government. Article Seven established the procedure used by the states to ratify it. The document was created by the Philadelphia Convention of 1787, ratified in 1788 and put into force in 1789. The original language of the articles and all amendments remain intact and can only be modified by a succeeding amendment. This practice was put into force with the first series of ten amendments ratified in 1791 known as the Bill of Rights, which specifies rights not defined in the seven articles of the constitution. There are twenty-seven amendments in all. Most of the later seventeen amendments have expanded civil rights protections or dealt with matters of federal authority and governmental processes and procedures. Only one amendment has been ratified that repealed another: the Twenty-first amendment repealed the Eighteenth Amendment to end Prohibition. Six amendments approved by congress and proposed to the states have not been ratified. Four of these are still pending, the oldest being the Congressional Apportionment Amendment proposed in 1789 to establish a formula to determine an appropriate size of the House of Representatives and a means to apportion the representatives among the sates following each decennial census.