In the first decades of the 20th century, mail bombs had yet to get headlines in the national press. Nevertheless, bombs did draw the attention of postal workers in other ways. In 1918, Chicago and the nation were in the midst of fierce debates over the nature of capitalism and the future of the nation. Self-proclaimed anarchists and labor activists involved in this debate turned to violence and the mail to make their point.
On September 4, 1918, someone tossed a bomb into the Adams Street entrance of the Chicago federal building and post office, killing four, including postal workers Edwin Kolkow and William Wheeler, and injuring dozens of others. The police focused their attention on members of the labor organization known as the Industrial Workers of the World (IWW). Officers rounded up and arrested almost 100 members of that group in the early days after the attack; all but a handful were released over the next few days. Despite intense investigations, no convictions ever came from the attack, nor a final reason for the bombing. On a side note, one of the many postal workers in the building at the time was a substitute letter carrier named Walt Disney.