Why wasn’t the Bill of Rights originally in the US Constitution?

When you think of the US Constitution, what’s the first thing that comes to mind? Free speech? The right to bear arms? These passages are cited so often that it’s hard to imagine the document without them. But the list of freedoms known as the Bill of Rights was not in the original text and wasn’t added for three years. Why not? James Coll goes back to the origins of the Constitution to find out.