This article compares marriage patterns by race, education and religion in the United States during the 20th century, using a variety of data sources. The comparative approach allows several general conclusions. First, racial endogamy has declined sharply over the 20th century, but race is still the most powerful division in the marriage market. Second, higher education has little effect on racial endogamy for blacks and whites. Third, the division between Jews and Christians is still strong, but the division between Catholics and Protestants in the marriage market has been relatively weak since the early 1900s. Fourth, educational endogamy has been relatively stable over time. (Contains 2 tables, 3 figures and 9 notes.)