Who wrote the United States Constitution? What role did James Madison play?

The Constitutional Convention occurred in 1787 with George Washington presiding.  James Madison created the foundational document for the U.S. Constitution.  He is considered the Father of the Constitution because of this.  Other Founding Fathers were also involved in the creation of the Constitution.  
James Madison's original document was called the Virginia Plan.  It contained a total of fifteen resolutions.  It discussed the separation of powers, which was a new idea compared to previous documents.  The document also suggested representatives based on population.
The ideas in the document which became the U.S. Constitution were also influenced by other great thinkers.  Thomas Paine and Thomas Jefferson were among those who wrote about liberty and freedom.  These ideas were important to the U.S. Constitution.  It is believed that a man named Gouverneur Morris put many of the ideas of the Constitution into words.  There were almost a dozen other men who also contributed to the writing and composition of the document.
https://www.archives.gov/founding-docs