We use linked U.S. Census data to study the intergenerational mobility of Jewish immigrants in the first half of the 20th century using Yiddish mother tongue as marker for Jewish origin. Across the distribution of fathers' occupational statuses, Jewish immigrants' sons climbed higher on the socioeconomic ladder than non-Jewish immigrants' and non-immigrant white Americans' sons. In addition, for Jewish sons, fathers' occupational status counted less for social ascent. Education played a critical role in this success. However, a residual `Jewish factor' accounts for as much as education in explaining achievements in earnings, entrepreneurship, or occupational status. We document the roles of network effects, family size, investment strategies, and geographical mobility as possible channels for such divergence in intergenerational mobility. No plausible amount of unobservable selection could cancel these results.