The United States Constitution was drafted in 116 days. The Constitutional Convention was a group of delegates from each state that gathered to write the Constitution. It convened on May 25, 1787 and adjourned on September 17, 1787.
While there were numerous discussions, drafts and rewrites of the Constitution, the final document was completed at the Constitutional Convention which lasted slightly more than 100 days. Delegates from all 13 colonies were chosen to attend, and George Washington was unanimously voted by those delegates to preside over the convention.
No one person wrote the Constitution; rather, it was a combination of efforts by all of the delegates in attendance. On July 24, 1787, a Committee of Detail was appointed by the delegates and, on August 6, 1787, this committee submitted a draft of the Constitution to the delegates at the convention for review and debate. On September 8, a new committee, the Committee of Style, was appointed by the convention to revise the draft. Finally, on September 12, 1787, this committee submitted the final draft of the Constitution to the delegates at the convention for approval.
A clerk by the name of Jacob Shallus was the penman who engrossed, or copied, the Constitution into its final form, the one most Americans are familiar with today. At the time, he was simply an assistant clerk of the Pennsylvania State Assembly. It is unlikely that he was ever aware of the importance of his job as he died in 1796 well before the Constitution became as important as it is today.