Every mass shooting, like the most recent at Santa Fe High School in Texas that left 10 people dead, reignites a passionate debate over the Second Amendment. For many Americans, if there is an image that comes to mind when they think about that amendment, it is the musket in the hands of minutemen at Lexington and Concord.

A dramatic but little-known story reveals that a more accurate image may be the musket in the hands of slave owners. It explains why, when he entered Congress and wrote a Bill of Rights, James Madison included a right to bear arms, and why it included the clause “A well regulated Militia, being necessary to the security of a free State …”

The story begins in June of 1788. Virginia was holding a convention in Richmond to decide whether to ratify the Constitution the founders had drafted in Independence Hall the previous year. Eight states out of the nine necessary to adopt the Constitution had already ratified, but Rhode Island, North Carolina, New Hampshire and New York looked unlikely to ratify. All hope for the ninth hung on Virginia.

The Virginia convention featured a dramatic debate between federalists, who favored ratification, and antifederalists, who opposed it. The debate pitted James Madison, a federalist and the principal drafter of the Constitution, against George Mason, the intellectual leader of the antifederalists, and Patrick Henry, Virginia’s governor and a renowned orator.