Leon Czolgosz (1873-1901) was an aspiring anarchist who assassinated President William McKinley in 1901. Czolgosz, who gravitated toward anarchist teachings after becoming involved in a series of labor disputes during the 1890s, convinced himself that he could best address the injustices he saw in American society by murdering the president. In September 1901, Czolgosz approached McKinley in a receiving line in Buffalo, New York, extending his arm as if to shake the president's hand before shooting him twice in the chest from point-blank range. McKinley died from his wounds a week later; Czolgosz was tried, convicted, and executed the following month.
Leon Czolgosz was not himself an immigrant, having been born in a small town in northern Michigan. But his parents had emigrated from Poland, and Czolgosz's non-anglicized name led many to believe, erroneously, that he was himself a foreigner. The assassination thus fueled widespread fears about the dangers posed by radical immigrants; in the wake of Czolgosz's crime, Congress passed new legislation making foreign-born anarchists and radical extremists ineligible for immigration or naturalization.