Although intermarriage is a common indicator of immigrant integration into host societies, most research has focused on how individual characteristics determine intermarriage. This study uses the 1910 ipums census sample to analyze how contextual factors affected intermarriage among European immigrants in the United States. Newly available, complete-count census microdata permit the construction of contextual measures at a much lower level of aggregation—the county—in this analysis than in previous studies. Our results confirm most findings in previous research relating to individual-level variables but also find important associations between contextual factors and marital outcomes. The relative size and sex ratio of an origin group, ethnic diversity, the share of the native-born white population, and the proportion of life that immigrants spent in the United State are all associated with exogamy. These patterns are highly similar across genders and immigrant generations.