1) The abolition of slavery in the United States was officially proclaimed with the ratification of the 13th Amendment to the Constitution in 1865.

2) The Berlin Conference in 1884-1885 divided Africa among European powers and set the stage for the colonization of the continent.

3) The Treaty of Tordesillas, signed in 1494, divided the newly discovered lands outside of Europe between Spain and Portugal, leading to the colonization of the Americas.

4) The Russian Revolution in 1917 resulted in the overthrow of the monarchy and the establishment of a communist government under Vladimir Lenin.