1919 United States anarchist bombings
From April through June 1919, a series of bombings were carried out or attempted across the United States by Galleanists (followers of Italian insurrectionary anarchist Luigi Galleani). The targets included anti-immigration politicians, anti-anarchist officials, and prominent businessmen, as well as a journalist and a church.
Source: Wikipedia — 1919 United States anarchist bombings (CC BY-SA 4.0)