The Constitution of the U.S. is the supreme law of the land, which means that when state constitutions or laws passed by state legislatures or by the national Congress are found to conflict with the federal Constitution, these laws have no force. It was completed on September 17, 1787, and was later ratified by special conventions in each state. It created a federal union of sovereign states, and a federal government to operate that union. It was Officially adopted on March 4, 1789 and has served as a model for the constitutions of other numerous nations. 
The Constitution consists of a preamble, seven original articles, and twenty-seven amendments. The preamble states its purpose, and the first three Articles of the Constitution establish the rules and separate powers of the three branches of the federal government: a legislature, the bicameral Congress; an executive branch led by the President; and a federal judiciary headed by the Supreme Court. The last four Articles frame the principle of federalism. The In:st ten constitutional amendments ratified by three-fourths of the states in 1791 are known as the Bill of Rights, which contains such liberties as freedom of religion, freedom of speech, freedom of press, the right of peaceful assembly, and the right to petition the government to correct wrongs, etc. The Constitution has been amended seventeen times (for a total of 27 amendments) and its principles are applied in courts of law by judicial review.