The USA first operated under an agreement called the Articles of Confederation (1781). The document set up a very weak central government, with too few powers for defense, trade, and taxation. There was no federal judiciary and no permanent executive. The individual states were almost independent. It was soon clear that this loose agreement was not working well and there was little to bind the 13 colonies together. Each individual colony started minting its own money, making its own laws and imposing duties on goods from other states. Some states were even preparing to establish their own army. This situation could cause a crisis. To prevent such crises, each state sent representatives (George Washington, Benjamin Franklin and James Madison among them) to Philadelphia in May 1787, to prepare a constitution. In 1789, the Constitution was written down. As the first president of the United States, George Washington was elected on 30 April, 1789. In 1791, first amendments, called the Bill of Rights, were added to the Constitution. The delegates decided that America would be a Republic with a president as a head of state. There would be two assemblies; an Upper House, called the Senate, and a Lower House, called the House of Representatives. Together the two houses were to be called Congress. The new Constitution also established the Supreme Court.