The Mail Building was constructed for Edward Warren in 1920 to house his growing newspaper publishing business. Warren had moved to Spearfish with his parents in 1888 hoping to start a newspaper, and in 1889 they established the Queen City Mail. The building was constructed of cast concrete blocks made from native sandstone material. Warren also served in the South Dakota legislature and as the Lawrence County Auditor. In 1929 he sold the newspaper to Arthur Nieselius, and in 1932 the Queen City Mail moved to a new building. The building then served as the U.S. Post office during the 1930s.