Karl Marx died in London at age 64, leaving Das Kapital unfinished and a body of ideas that would reshape the twentieth century.

Robert Koch, working in Egypt and Calcutta, announced isolation of Vibrio cholerae, the bacterium responsible for cholera, transforming public health responses to the disease.

The Brooklyn Bridge opened to the public, its 1,595-foot main span the longest suspension bridge in the world, linking Manhattan and Brooklyn for the first time.

The volcanic island of Krakatoa tore itself apart in a series of cataclysmic explosions, the loudest sound ever reliably recorded, heard 3,000 miles away.

The Orient Express departed Paris's Gare de l'Est for the first time, bound for Constantinople, inaugurating an era of glamorous long-distance rail travel across Europe.