In America, he spent most of his professional life in New York City, where he helped found the American Jewish Committee in 1906. Magnes was also one of the most influential forces behind the organization of the Jewish community in the city, serving as president throughout its existence from 1908 to 1922. The "Kehillah" oversaw aspects of Jewish culture, religion, education and labor issues, in addition to helping to integrate America's German and East European Jewish communities. He was also the president of the Society for the Advancement of Judaism from 1912 to 1920.