Dedicated in 1893, it commemorates the defendants involved in labor unrest who were blamed, convicted, and executed for the still unsolved bombing during the Haymarket Affair (1886).

There is a two step base, which also supports a pedestal and a monumental figure of Justice, depicted as a woman standing guard over the body of a fallen worker, both in bronze.

On the first step, there is a quote attributed to Spies, recorded just before his execution by hanging: "The day will come when our silence will be more powerful than the voices you are throttling today."

Above the names, a bronze plaque contains text of the pardon later issued by Governor John Peter Altgeld of Illinois.

According to a list in the records of the Pioneer Aid and Support Association, the lost time capsule is to contain newspaper articles, letters to and from the Haymarket defendants, and photographs of the men and their families.

[5] The group that discovered the urn cylinder also found a smaller concrete cube thought to be a cremation vault for the ashes of Haymarket martyr Oscar Neebe, pardoned by Gov.