Born in Elberfeld, Germany, son of George Marx, a banker, and Gertrud Marx-Simon, a published poet.
In 1903, Marx accepted Solomon Schechter's invitation to teach history at the Jewish Theological Seminary of America and be its librarian.
This pioneering work, stressed economic and social life, organization and legal status.
It offers the reader a soundly researched, authoritative, and objective Jewish history in one volume.
At his death it possessed 165,000 books and over 9,000 Hebrew, Samaritan, Aramaic, and Yiddish manuscripts, comprising the largest Judaica collection in the world.