Colorado coal miners and militia clashed for days after the Ludlow Massacre, part of a labor war that culminated in fighting around April 22.

Gavrilo Princip shot Archduke Franz Ferdinand and his wife Sophie in Sarajevo, an assassination that triggered a chain reaction leading to World War I.

The cargo ship SS Ancon made the first complete official transit of the Panama Canal, completing a decade-long engineering feat that reshaped global trade.

Austria-Hungary declared war on Serbia one month after the assassination of Archduke Franz Ferdinand, igniting the chain of alliances that became World War I.

Britain declared its policy toward neutral shipping and began the naval mobilization that would shape the opening months of World War One at sea.

The cargo ship SS Ancon made the first official transit of the Panama Canal, completing a 51-mile passage that reshaped global trade and naval power.

The SS Ancon became the first ship to officially transit the newly completed Panama Canal, linking the Atlantic and Pacific Oceans through 51 miles of locks and channels.

The SS Ancon became the first ship to make a full official transit through the newly completed Panama Canal, linking the Atlantic and Pacific oceans.

The SS Ancon made the first official transit through the newly completed Panama Canal, linking the Atlantic and Pacific oceans after a decade of construction.

The SS Ancon becomes the first ship to officially transit the newly completed Panama Canal, linking the Atlantic and Pacific oceans.

Marcus Garvey establishes the Universal Negro Improvement Association in Kingston, Jamaica, launching a movement for Black pride and Pan-African unity.

German and British soldiers along the Western Front laid down arms, sang carols across no-man's-land, and met to exchange gifts and bury their dead.

In the final stretch of the informal 1914 Christmas Truce, German and British troops along the Western Front held joint burial services and sang carols across no-man's-land.