The United States has admitted more than 3 million refugees since 1980 through official refugee resettlement programs. Scholars attribute the success of refugee groups to governmental programs on assimilation and integration. Before 1948, however, refugees arrived without formal selection processes or federal support. We examine the integration of historical refugees using a large archive of recorded oral history interviews to understand linguistic attainment of migrants who arrived in the early twentieth century. Using fine-grained measures of vocabulary, syntax and accented speech, we find that refugee migrants achieved a greater depth of English vocabulary than did economic/family migrants, a finding that holds even when comparing migrants from the same country of origin or religious group. Our findings are consistent with the hypothesis that refugees had greater exposure to English or more incentive to learn, due to the conditions of their arrival and their inability to immediately return to their origin country.