The event marked by the assassination of President McKinley was the beginning of a shift in American politics, particularly regarding the progressive movement. McKinley was shot by anarchist Leon Czolgosz on September 6, 1901, and succumbed to his injuries on September 14, 1901. His assassination led to the ascension of Vice President Theodore Roosevelt, who embraced progressive ideals and pushed for reforms. This transition marked a significant turning point in U.S. domestic and foreign policy, leading to enhanced regulation of corporations, labor rights, and social reforms that would shape the early 20th century.