The early 20th century had much in common with our time. It was an epoch of great extremes of wealth and poverty, of globalization and free trade, of war and imperialist occupation. But one crucial difference stands out: it was also a time of great militancy by the radical working class. And nowhere was this more apparent than in San Francisco on the eve of World War One, when a bomb exploded during a pro-war parade on Market Street. Joseph Matthews discusses the class war in San Francisco, a century ago.