April 19 is a heavy day in history. Fifteen years ago, a truck bomb blasted through the Alfred P. Murrah Federal Building, claiming the lives of 168 people.

Two years prior, April 19 marked the end of the 51-day siege of the Branch Davidian compound in Waco, Texas, which ended when a fire destroyed the building, killing all 76 people inside. The Waco Siege allegedly motivated Timothy McVeigh, one of the architects of the Oklahoma City bombing, to carry act this act of domestic terror.

If that weren’t enough, tomorrow, April 20, is the 11th anniversary of the Columbine High School massacre. In 1999, two seniors entered their school armed with shotguns and semi-automatic firearms and killed 12 students and a teacher. According to reports that followed the tragedy, the shooters had originally planned to carry out their rampage on April 19.

The history of discord on April 19 even goes back to the beginning on the American Revolution when, in a more celebrated act of violence in 1775, the first shots were fired at the battles of Lexington and Concord.

The date also marks the occasion that Nazi soldiers raided a Warsaw ghetto to round up innocent Jews.

Although these events appear entirely disconnected, some anti-government groups, particularly at the fringes, have come to view these incidents as emblematic of the fight against authoritarian repression. Even today, gun rights advocates are descending on Washington, D.C.

This year that sentiment seems to be resonating among a larger and growing group of people.

The Southern Poverty Law Center, based in Montgomery, Ala., claims the number of militia groups, which it refers to as “extremist,” grew from 149 to 512 between 2008 and 2009. And it’s not just militias. According to a poll released by the Pew Research Center today, nearly a third of Americans view the government as a “major threat” to their freedoms.

With such apparent rising discontent brewing in the country, should we brace for more violence? Perhaps it’s better, instead, to celebrate all those other — nonviolent — April 19′s in history. After all, they far outnumber the violent ones.

Here’s to a quiet day.

Photo: Family members of victims of the Oklahoma City bombing gather at a memorial. Credit: Getty Images

Discovery News’ Amanda Onion contributed to this story.