From the campaign:
On 16th January, 1919 the government passed a bill whose noble goal was to improve the quality of life and the health of the citizens of the United States. The Noble Experiment, as it is called today (or Prohibition in the USA back in the day), has turned out to be a fiasco and had a number of side effects.
One of those side effects was the creation of a moonshine black market and the blooming of organized crime. While playing '1919: The Noble Experiment' you shall assume the leadership of such a ragtag band of mobsters.