The first celebration of this holiday took place a year after New Orleans police chief David Hennessy was killed and 11 Italian-Americans were lynched in retaliation.  
Angelo Noce led a campaign to make Colorado the first state to officially commemorate this event.  During a parade commemorating this event, an in-costume Joseph Cervetto, Jr. once waved his replica sword to mock a crowd in San Francisco that was trying to disrupt the parade and throwing Molotov cocktails.  Federal commemoration of this event was achieved thanks to the work of an organization founded by Michael J. McGivney; that (*) Catholic organization is named after this event's central figure.  The first celebration of this holiday took place a year after New Orleans police chief David Hennessy was killed and 11 Italian-Americans were lynched in retaliation.  This event is commemorated on a day that is also celebrated as Canadian Thanksgiving and Indigenous People's Day.  For 10 points, name this event commemorated in the United States on the second Monday in October.
Angelo Noce led a campaign to make Colorado the first state to officially commemorate this event.  
Christopher Columbus' discovery of the New World (accept anything involving Columbus and landing in the New World; accept Knights of Columbus or Columbus Day)