Polish-born anarchist Leon Czolgosz shoots and fatally wounds U.S. President William McKinley at the Pan-American Exposition in Buffalo, New York. McKinley dies September 12, and Czolgosz is later executed.

The Neutrality Acts, which had been passed in the 1930s when the United States considered foreign conflicts undesirable, prompts the nation to declare neutrality in World War II. The policy ended with the Lend-Lease Act of March 1941, which allowed the U.S. to sell, lend or give war materials to allied nations.

During the 1972 Summer Olympics in Munich, West Germany, a paramilitary group calling itself Black September takes members of the Israeli olympic team hostage. Eventually the group, which represents the first glimpse of terrorists for most people in the Western world, kill eleven of the hostages along with one West German police officer during a rescue attempt by West German police that devolves into a firefight. Five of the eight members of Black September are also killed.

The governor of Arkansas, Orval Faubus, mobilizes the National Guard to prevent nine African-American students known as the Little Rock Nine from enrolling in high school in Little Rock, Arkansas.

Auschwitz-Birkenau, the largest of Nazi Germany’s concentration camps, becomes an extermination camp when it begins using poison gas to kill prisoners en masse. The camp commandant, Rudolf Höss, later testifies at the Nuremberg Trials that he believes perhaps 3 million people died at Auschwitz, but the Auschwitz-Birkenau State Museum revises the figure to about 1 million.