The Chamberlain American Legion was originally chartered on July 7, 1919 and designated as Potter Post 3. The first commander was C.A. Whitbeck, Adjutant was J.W. Lewis, Treasurer A.J. Gilbert, Service Officer was G.C. Uhler, Chaplain was Rev. Robert Frazier, Historian was C.A. Knight and Secretary was R.W. Gano. The total number of enrolled members the first year was 125 with dues being $3. The post was named after Carl and Oscar Potter, two brothers from Chamberlain who died in WWI. Carl Potter, the younger of the two brothers entered the service in June 1918 and following training became a member of the Infantry. He died in France on October 4, 1918 from pneumonia. Oscar Potter entered the service in May 1918. Following training he left for overseas, a member of a machine gun battalion. He was mortally wounded in action during the last drive of the Argonne on November 9, 1918 and died the following day, one day before the Armistice was signed.
For the purposes of holding legal title to all real property held or owned by the American Legion or Ladies Auxiliary of Chamberlain, Article of Incorporation and bylaws were properly filed with the State of South Dakota in October 1954 with legal corporate name of Potter Post Legion and Auxiliary Holding Company. The business and property of the organization was to be managed by six trustees elected from the membership. The original six trustees were: Harry Plott, A.R. Newman, Alice Dyca, Iva Hemphill, Bertha Wedmore and Donald Porter.
In January 1964, new Articles of Incorporation were adopted changing the mane to Potter Post No 3 of the American Legion. The five directors at that time were: Joe Beyer, H.B. Schelle, Ben Lewis, Leland Chilson and Melvin Goetsch.
Potter Post 3 has sponsored an American Legion Baseball team for many years as well as representatives to Boys State.