On this day in 1906, revolutionary anarchist Mateu Morral attempted to assassinate Spanish King Alfonso XIII and his bride via bomb. The attack failed, killing 24 bystanders, and caused state persecution of other anarchists.

Image: Photograph of the assassination attempt on King Alfonso XIII and Victoria Eugenia at the moment of the bomb's explosion [Wikipedia]

On this day in 1921, the Tulsa Race Massacre began when mobs of white people attacked residents and businesses of the Greenwood District, known as "Black Wall Street", killing hundreds and rendering 10,000 black families homeless.

Image: A photo showing the aftermath of the Tulsa Race Massacre, showing a city block razed to the ground. From the Universal History Archive [mashable.com]