What happened at the Constitutional Convention?

Why this is the answer

The Constitution was written there, and either accepted answer says so. The convention met in Philadelphia from May to September 1787, with fifty-five delegates from twelve of the thirteen original states; Rhode Island stayed away. They had been sent to amend the Articles of Confederation, because the national government those Articles created was too weak, but they concluded that patching it was not enough and wrote an entirely new governing document instead. They worked four months in secret so that discussion could be free, and on September 17, 1787, thirty-nine delegates signed. The delegates are the ones we call the Framers. Memory hook: they went to fix the Articles and came back with the Constitution.