The Constitutional Convention drafted the Constitution of the United States. The delegates to the convention met in Liberty Hall, in Philadelphia, Pennsylvania, beginning May 25, 1787. Thirty-nine of the delegates signed the Constitution on September 17. The Constitution replaced the Articles of Confederation, the new nation’s first constitution. The Articles had given the country a weak central government. The new Constitution gave the country a strong government.

The Second Continental Congress and some states called for the convention. They did this in response to several serious situations. First, Congress was about to go bankrupt. Second, an armed revolt—Shays’s Rebellion—in Massachusetts had raised fears around the country.

These situations, and others, led many people to call for a stronger national government. To do this, the Articles of Confederation would have to be amended (changed). This document had been the nation’s basic law since 1781. But it had not created a strong government. Each state had kept its sovereignty (self-government), freedom, and independence.

A few states had tried to amend the Articles at the Annapolis Convention in 1786. Now the Constitutional Convention was supposed to take on that task. But instead of trying to fix the Articles, the delegates wrote a new constitution.

Fifty-five delegates from 12 states (all except Rhode Island) attended at least some of the sessions. Thirty-four of them were lawyers. Most of the others were planters or merchants. George Washington, who presided, was 55. John Dickinson was 54. Benjamin Franklin was 81. And Roger Sherman was 66. But most of the delegates were young men in their twenties and thirties.

Noticeably absent were the radical leaders of the drive for independence in 1775–76. John Adams was not there. Nor were Patrick Henry and Thomas Jefferson.

The first phase of the convention lasted from May 25 to July 26. The delegates developed the general outlines of a national government. They agreed to create a government with three branches: legislative, executive, and judicial. James Madison was the strongest supporter of this type of government. He would later become known as the "Father of the Constitution."

The delegates, however, were divided over how the states should be represented in the legislative branch—the Congress. Three plans were put forward.

The Virginia Plan called for a bicameral (two-house) legislature—an upper house (Senate) and a lower house (House of Representatives). Representation in both houses would be according to each state’s population. This proposal clearly favored the larger states.

The New Jersey Plan provided for a unicameral (one-house) legislature. In this plan, all the states would be represented equally.

The Connecticut Compromise settled the issue. It called for a bicameral legislature. It gave the states equal representation in the Senate. And it based representation in the House of Representatives on population.

The second phase of the convention lasted from July 27 to August 6. During this phase, a five-man Committee of Detail drew up a rough draft of the Constitution.

During the third phase (August 6–September 6), the delegates debated the committee's draft. They fought over conflicting interests. There were, for example, conflicts between commerce and agriculture. There were conflicts between slaveholders and others.

The most controversial issue was the composition of the executive branch and the means of electing the chief executive (president). This was settled on September 6 with the adoption of the electoral college. It had been suggested by Benjamin Franklin.

The last phase of the convention was mainly the work of the Committee on Style, headed by Gouverneur Morris. This group of delegates put the document in finished form.

On September 17, 1787, the Constitution was signed by 39 of the 42 delegates present. A period of national debate followed.

The case for support of the Constitution was forcefully presented in The Federalist essays. These articles were written by Alexander Hamilton, John Jay, and James Madison. At least 9 states had to ratify (formally approve) the Constitution for it to become law. New Hampshire was the ninth, on June 21, 1788. The last of the 13 states to ratify the Constitution was Rhode Island, on May 29, 1790.