American Protective League

The American Protective League (1917–1919) was an organization of private citizens sponsored by the United States Department of Justice that worked with federal law enforcement agencies during the World War I era. Its mission was to identify suspected German sympathizers and to counteract the activities of radicals, anarchists, anti-war activists, and left-wing labor and political organizations. At its zenith, the APL claimed 250,000 members in 600 cities.