1851 On 9 April, police officials from Austria, Prussia, Sachsen, and Hannover gather to create an international police organization for political purposes. Within a year, they are joined by police from Bavaria, Wurttemberg, and Baden to form the Police Union of German States.
At least thirty-five foreign police officials, including several city police officers from the United States, attend the International Industrial Exhibition in London to investigate the activities of communists and liberals.
1851–1866 Members of the Police Union hold twenty meetings and establish direct police communications and systems of information exchange until the outbreak of the Austro-Prussian War (June 15 to August 23 1866).
1871 In October, a three-day National Police Convention is held in St. Louis, Missouri. Despite the fact that several European police were invited to attend the meeting, the convention remains an exclusively American affair.
1898 From 24 November to 2 December, the International Conference of Rome for the Social Defence Against Anarchists is held. The Conference is attended by fifty-four delegates from twenty-one European states. Police officials hold separate meetings at the Conference and agree to cooperate on selected matters of policing techniques.
1901 To broaden the scope of the National Police Chiefs' Union, the organization is renamed the International Association of Chiefs of Police.
At the Second Latin-American Scientific Congress in Montevideo, Uruguay, Juan Vucetich, Police Chief in La Plata, Argentina, proposes the establishment of an interconnected system of Intercontinental Offices of Identification in Europe, South America, and North America.
1902 On 15 July, the French government organizes an international conference in Paris to coordinate the suppression of prostitution and establish extradition procedures.
1903 As a follow-up to the Rome Conference of 1898, a second anti-anarchist meeting is organized by the Russian government in St. Petersburg, where ten governments agree upon a Secret Protocol for the International War on Anarchism.
As a follow-up to the conference of 1902, a second antiprostitution meeting is held in Paris, where twelve European governments sign an International Agreement for the Suppression of White Slave Traffic.
1905 At a meeting in Hamburg, the International Union of Criminal Law (Internationale Kriminalistische Vereinigung) advocates the creation of interrelated central intelligence bureau...