Immigrant populations typically have lower mortality rates and longer life expectancies than their nonimmigrant counterparts. This immigrant mortality advantage has been a recurrent finding in demographic and population health research focused on contemporary waves of immigration. However, historical data suggest that European immigrants to the United States in the early twentieth century had worse health and higher rates of mortality, yet it remains unclear why a mortality advantage was absent for immigrants during this period. This article combines Vital Statistics records and Lee–Carter mortality models to analyze mortality by nativity status for the U.S. White population from 1900 to 1960, examining variation by age, sex, time, and place. Contrary to contemporary expectations of a foreign-born mortality advantage, White immigrants had higher mortality rates in the early 1900s, with the largest foreign-born disadvantage among the youngest and oldest populations. Although foreign-born and U.S.-born White mortality rates trended toward convergence over time, the foreign-born mortality penalty remained into the 1950s. A decomposition analysis finds that immigrants’ concentration in cities, which had higher rates of infectious disease mortality, accounted for nearly half of the nativity difference in 1900, and this place effect declined in subsequent decades. Additional evidence, such as a spike in mortality inequalities during the 1918 influenza pandemic, suggests that common explanations for the immigrant mortality advantage may be less influential in a context of high risk from infectious disease.