Although the terrorist attacks of 11 September 2001 shocked the world, America has confronted terrorism at home for well over a century. With the invention of dynamite in 1866, Americans began to worry about anonymous acts of mass violence in a way that differed from previous generations' fears of urban riots, slave uprisings, and mob violence. Focusing on the volatile period between the 1886 Haymarket bombing and the 1920 bombing outside J. P. Morgan's...