The American Civil Liberties Union was formed in January 1920 by Roger Baldwin. Baldwin, a social worker and native of Boston, moved to St. Louis from Boston in 1906 where he taught the first course in sociology at Washington University; was the first director of the Self-Culture Hall, a neighborhood settlement house founded by the Ethical Society of St. Louis; served as secretary of the St. Louis Civic League, an organization of urban progressives; worked successfully for progressive reform of the juvenile court system and counseled pacifists at the outbreak of the First World War. Baldwin stated, “When I read of the British conscientious objectors in the war,” he recalled, “I knew I was one of them.”
In 1916 Roger Baldwin joined the St. Louis affiliate of the American Union Against Militarism (AUAM) and in the spring of 1917 he resigned his position with the Civic League and moved to New York in order to donate his services to the AUAM national directing committee. In May of the same year, Baldwin organized the Bureau for Conscientious Objectors as a sub-agency of the AUAM to advise objectors about legal technicalities and in other ways provide legal or economic assistance. Due to ideological differences, Baldwin’s organization broke away from the AUAM and became the National Civil Liberties Board, an independent association.
In the fall of 1918, just as the war was about to end, Baldwin went to prison for eight months for violating the draft law. He was released in 1919 and in 1920 was instrumental in the organization of the American Civil Liberties Union.
In that same year, a small group of St. Louisans formed the St. Louis Civil Liberties Committee (StLCLC), described as a "permanent non-profit, non-partisan organization devoted to defending the liberties guaranteed by the Bill of Rights." The StLCLC's 1936 Constitution lists its purpose as the furtherance of the cause of freedom of speech, writing, publication, assembly and thought by all legitimate means; the protection of the legal rights of individuals in respect to such instances as may be deemed worthy; the promotion or opposition of legislation and other official action bearing upon civil liberties; and cooperation to the fullest extent possible with the American Civil Liberties Union in such of its activities as meet with the approval of the StLCLC.
The StLCLC changed its name to the American Civil Liberties Union of Eastern Missouri (ACLU-EM) in 1968.
On Oct. 1, 2013, the ACLU-EM became the ACLU of Missouri and now has responsibility for the entire state.