The United States hasn't seen a school massacre of this scale since — which makes it all the more surprising that most of us know nothing about it.

From the Titanic to the moon landing, these rarely-seen historical photos reveal how things looked just before history was made.

These World War 1 propaganda posters courtesy of the U.S. government provide a fascinating look at the America of a century ago in the midst of the Great War.

If the United States can teach us one thing, it's that diplomacy has its limits.

From Pearl Harbor to D-Day to the momentous events you may not know so well, these World War 2 photos bring history's worst cataclysm to life.

The Great Depression hit few cities harder than New York — but the city's darkest hour was also the crucible in which today's New York was forged.

These stark, heart-wrenching Dust Bowl pictures reveal both the vast scope and intimate despair of this tragic time.

From the assassinations of MLK and RFK to antiwar and civil rights protests nationwide, these 1968 photos reveal a nation at war with itself.

Over the course of 500 bloody years, the Native American genocide carried out by both European settlers and the U.S. government left millions dead.

From Operation Teardrop to the Biscari massacre, these are the atrocities that the U.S. would rather forget.