A Philadelphia lawyer, Lucien Alexander came from a wealthy Scots-Irish family with strong ties to the lumber, oil, and railroad industries in Pennsylvania. After receiving his education at the University of Pennsylvania (1884-1887) and Harvard (1887-1888), Alexander entered into the offices of William Henry Rawle and Alonzo Tillinghast Freedley to study law, earning admittance to the Pennsylvania bar in 1896. During a comparatively brief career in active litigation, he handled some very high profile cases, most notably representing Robert Peary in his dispute with Frederick A. Cook over priority in the "discovery" of the North Pole. Alexander ceased general practice in 1909 to assume a position as special counsel for four Midwestern railroad corporations.
Alexander's legacy, however, lies less in his skills as a litigator, than in his tireless efforts during the first decade of the twentieth century to further the professionalization of legal practice. As a young member, and later secretary of the board of examiners controlling admission to the Philadelphia bar, Alexander helped initiate several quintessentially progressive reforms, including the addition of a written examination to the bar exam, along with a general educational examination and inquiries into the moral character of candidates. His efforts to extend these reforms statewide resulted in the establishment of the state board of law examiners.
With the support of the American Bar Association, Alexander continued his campaign for professional reform at the national level, meeting with a similar degree of success. As chair of the first A.B.A. committee to formulate standards for admission to the bar and as secretary to the committee to draft a professional code of ethics, Alexander helped to write two reports that in 1908, became the basis for substantial professional reforms. He was instrumental, as well, in the establishment of the American Bar Association Journal (1915), in the formation of the American Institute of Law (1923), and in promoting legal research and scholarship. He was married twice, to Mazie Just in 1888, and Anna Harris in 1920. Anna and his four children (three by his first marriage) all survived Alexander's death on April 6, 1926.