This biographical study analyzes the careers and thinking of a dozen union leaders of Irish descent who contributed significantly to the union movement. The work demonstrates the pragmatic approach of the majority of these leaders arising from disappointing experience with radical ideas embraced in their youth. Their object was cohesion among diverse nationalities in the work force to build strong national unions able to eliminate destructive wage competition in ever-widening markets. Beginning with background on Irish immigration, the study follows developments from the 1870s and extends through those who were active in the 1950s on both coasts and in the mid-west. It is the first book written for scholars and others dealing with Irish-American unionists in depth.