<P> These and other issues greatly worried many of the Founders that the Union as it existed up to that point was in danger of breaking apart, and being subject to the persuasion of foreign powers . </P> <P> In September 1786, at the Annapolis Convention, delegates from five states called for a Constitutional Convention in order to discuss possible improvements to the Articles of Confederation . The subsequent Constitutional Convention took place in Philadelphia, convening in the Old Pennsylvania State House (then becoming known as Independence Hall) on May 14, 1787 . Rhode Island, fearing that the Convention would work to its disadvantage, boycotted the Convention and, when the Constitution was put to the states during the next year of controversial debates, initially refused to ratify it, waiting until May 1790 to become the thirteenth, a year after the new federal government commenced . </P> <P> Due to the difficulty of travel in the late 18th century, very few of the selected delegates were present on the designated day of May 14, 1787, and it was not until May 25 that a quorum of seven states was secured . (New Hampshire delegates would not join the Convention until more than halfway through the proceedings, on July 23 .) James Madison arrived first, and soon most of the Virginia delegation arrived . While waiting for the other delegates, the Virginia delegation produced the Virginia Plan, which was designed and written by James Madison . On May 25, the delegations convened in the Pennsylvania State House . </P> <P> George Washington was unanimously elected president of the Convention, and it was agreed that the discussions and votes would be kept secret until the conclusion of the meeting . Despite the sweltering summer heat, the windows of the meeting hall were nailed shut to keep the proceedings a secret from the public . Although William Jackson was elected as secretary, his records were brief and included very little detail . Madison's Notes of Debates in the Federal Convention of 1787, supplemented by the notes of Robert Yates, remain the most complete record of the Convention . Throughout the debate, delegates constantly referred to precedents from history in support of their position . Most commonly, they referred to the history of England, in particular the Glorious Revolution (often simply called "The Revolution"), classical history (mainly the Roman Republic and the leagues of Greek city - states), and recent precedents from Holland and Germany . </P>

The constitutional convention of 1787 in philadelphia occurred in which century