The United States celebrates Constitution Day on the 17th of September. On that day in 1787, thirty-nine delegates to the Constitutional Convention in Philadelphia signed the Constitution of the United States. Among the important consequences of that action was the creation of the United States Senate. This would not have been possible without the Great Compromise reached one month earlier, which established the basis of representation in the Senate and House of Representatives, ending a dispute between the large and small states. New Hampshire adopted the Constitution on June 21, 1788, becoming the necessary ninth state to ensure the document's ratification. The following September, the Pennsylvania legislature elected William Maclay and Robert Morris, the first United States senators chosen under the new Constitution. In 2004, Senator Robert C. Byrd introduced and the Senate passed legislation to establish a yearly celebration of "Constitution Day." Learn more about the Constitution.