Unitarian minister Joseph Priestley was a well known radical philosopher, theologian, historian, scientist, and reform writer. An important member of the Dissenting circle that frequented Joseph Johnson's publishing establishment, he was also a particularly close friend of Anna Letitia Barbauld. During the 1791 "church and king" riots in Birmingham, Priestley's home and laboratory were destroyed by the mob, and in 1794 he emigrated to America.