Founded in 1841, the London Library occupied a unique position in the intellectual landscape of Victorian London, offering books "in all departments and in all languages" for loan to subscribing members. John Stuart Mill was a founder lifetime member of the library. A forensic examination of his membership is presented. Bibliographic details of volumes borrowed from the library by Mill, and books, pamphlets and tracts donated by him have been identified, and have been triangulated with a digital corpus of his monographs. A direct relationship between the books Mill borrowed and his oeuvre is evidenced. The intersection between Mill's donations and his role on the national and international stage is demonstrated in relation to his intellectual interventions during the Irish Famine and the American Civil War. A case is posited for the international significance of the collection.