This past Saturday marked a very sad anniversary and one that continues to have reverberations across the nation. On April 20, 1999, two disturbed young men, Dylan Klebold and Eric Harris, began gunning down their fellow students outside of Columbine High School in Littleton, Colorado, a suburb south of Denver. Klebold and Harris then moved inside the school building and, by the time they were finished, they had killed a dozen students and one teacher and wounded more than 20 others. Less than an hour after the first shot was fired, the pair turned their guns on themselves, ending the carnage.

But the tragedy didn’t end for America. Although school shootings predate the birth of our nation (in 1764, during Pontiac’s Rebellion, four Native American warriors entered a schoolhouse in Pennsylvania and killed nine or 10 students and the schoolmaster), the Columbine massacre represents a turning point in modern history.

If you are looking for the lasting impact of the Columbine...