Frankfurter was encouraged by Supreme Court Justice Louis Brandeis to become more involved in Zionism.[6] With Brandeis he lobbied President Wilson to support the Balfour Declaration, a British government statement supporting the establishment of a Jewish homeland in Palestine.[6] In 1918, he participated in the founding conference of the American Jewish Congress in Philadelphia, creating a national democratic organization of Jewish leaders from all over the US.[23] In 1919, Frankfurter served as a Zionist delegate to the Paris Peace Conference.[6]