When delegates in nine of the then thirteen states ratified the document, it marked the creation of a union of sovereign states, and a federal government to administer that union. It took effect on March 4, 1789, replacing the weaker, non-centralized union that existed under the Articles of Confederation. The Constitution of the United States is one of the oldest constitutions still in use (the oldest being that of the Republic of San Marino, which dates backs to 1600), and the oldest federal constitution currently in use.
In September 1786, commissioners from five states met in the Annapolis Convention to discuss adjustments to the Articles of Confederation that would improve commerce. They invited state representatives to convene in Philadelphia to discuss improvements to the federal government. After debate, the Confederation Congress endorsed the plan to revise the Articles of Confederation on February 21, 1787. Twelve states, Rhode Island being the only exception, accepted this invitation and sent delegates to convene in May 1787. The resolution calling the Convention specified its purpose was to propose amendments to the Articles, but the Convention decided to propose a rewritten Constitution. The Philadelphia Convention voted to keep deliberations secret and decided to draft a new fundamental government design which eventually stipulated that only 9 of the 13 states would have to ratify for the new government to go into effect (for the participating states). Congress, noting dissatisfaction with the Articles of Confederation government, unanimously agreed to submit the proposal to the states despite what some perceived as the exceeded terms of reference. On September 17, 1787, the Constitution was completed in Philadelphia, followed by a speech given by Benjamin Franklin. In it he talked about how he wasn't completely satisfied with it but that perfection would never fully be achieved. He accepted the document as it was and he wanted all those against the ratification of it to do the same. After fierce fights over ratification in many of the states, New Hampshire became that ninth state on June 21, 1788. Once the Congress of the Confederation received word of New Hampshire's ratification, it set a timetable for the start of operations under the Constitution, and, on March 4, 1789, the government under the Constitution began operations.
Changes since 1787
The Bill of Rights comprises the first ten amendments to the Constitution. Those amendments were adopted between 1789 and 1791, and all relate to limiting the power of the federal government.
First Amendment: addresses the rights of freedom of speech, freedom of the press, the freedom of assembly, freedom of petition, and also freedom of religion, both in terms of prohibiting the Congressional establishment of religion and protecting the right to free exercise of religion.
Second Amendment: declares the necessity for "a well regulated militia," and prohibits infringement of "the right of the people to keep and bear arms."
Third Amendment: prohibits the government from using private homes as quarters for soldiers without the consent of the owners. The only existing case law regarding this amendment is a lower court decision in the case of Engblom v. Carey.
Fourth Amendment: guards against searches, arrests, and seizures of property without a specific warrant or a "probable cause" to believe a crime has been committed. Some rights to privacy have been inferred from this amendment and others by the Supreme Court.
Fifth Amendment: forbids trial for a major crime except after indictment by a grand jury; prohibits repeated trials for the same offense after an acquittal (except in certain very limited