On September 23, 1901, Leon Czolgosz was put on trial for assassinating US President William McKinley at the Pan-American Exposition in Buffalo, New York. Learn more about the legal aftermath of the McKinley assassination from the University of Buffalo Libraries.

On September 23, 1905, negotiations on the Karlstad Treaty ended with an agreement to split the union of Sweden and Norway. The accord was then approved by Norway's parliament on October 9 and by Sweden's on October 13. Learn more about the former Union of Sweden and Norway.