The United States Constitution was written at the 1787 Philadelphia Convention and ratified by the states in 1788, taking effect in 1789. During the 1780s, the United States had operated under the Articles of Confederation, which was essentially a treaty of thirteen sovereign states. Domestic and foreign policy challenges convinced many in the United States of the need for a new constitution that provided for a stronger national government. The supporters of ratification of the Constitution were called Federalists while the opponents were called Anti-Federalists. The immediate problem faced by the Federalists was not simply one of acceptance of the Constitution but the more fundamental concern of legitimacy for the government of the new republic. With this challenge in mind, the new national government needed to act with the idea that every act was being carried out for the first time and would therefore have great significance and be viewed along the lines of the symbolic as well as practical implications. The first elections to the new United States Congress returned heavy Federalist majorities. George Washington, who had presided over the Philadelphia Convention, was unanimously chosen as the first President of the United States by the Electoral College.