Measuring spouses’ ages allows us to explore larger sociological issues about marriage, such as whether narrowing gaps signal gender progress or if a rise in female-older unions reveals a status change. Using Census and American Community Survey data, I test the merits of beauty-exchange and status homogamy theories as explanations for how heterosexual marital age gaps changed over a 40-year period of social and economic revolution. Analyses address questions about how age gaps compared for people with different characteristics, whether similarly aged couples exhibited greater educational and socio-economic homogamy than others, and if the odds of being in age-heterogamous marriages changed. Chapter 4 provides the historical context of U.S. marriages from 1910 on, and shows that while disadvantaged groups retreated from marriage, the percentage of individuals with greater education and income who married remained high. Age homogamy rose over 100 years due to a decline in marriages involving much-older husbands rather than increases in wife-older unions. Results in Chapter 5 show that mean age gaps decreased significantly over time for first-married individuals by most—but not all—characteristics. Gaps narrowed for those who were White, Black, other race, or of Hispanic origin; from any age group; with zero, one, or two wage earners; with any level of education; and from most types of interracial pairs. One exception was that mean age gaps increased between Asian wives and White husbands, and Asian women’s odds of having a much older husband were higher than the odds for racially homogamous women. Those odds increased over time. Findings lent support for status homogamy theory, since same-age couples showed greater educational homogamy than others in any decade, but showed mixed support for beauty exchange. In 2010-14, the median spousal earnings gap was wider in husband-older marriages than age-homogamous ones; however, the reverse was true in 1980. Women-older first or remarriages exhibited the smallest median earnings gaps in 1980 and 2010-14, and women in these marriages contributed a greater percentage of the family income than other women in 2010-14 (43.6% vs 36.9%, respectively). The odds of being in age-heterogamous unions were significantly higher for persons who were remarried, from older age groups, from certain racial backgrounds, in some interracial marriages, less educated, and from lower SES backgrounds. Age and remarriage showed the greatest impact on odds ratios. While age homogamy increased overall, the odds of being a much older spouse (11+ years older) increased dramatically for remarried men and women between 1970 and 1980, and then remained high in 2010-14. Remarried women’s odds of being the much older wife versus a same-age spouse were 20.7 times that of the odds of first-married women in 2010-14. Other results showed that Black men’s odds of being with a much-older wife compared to one around the same age were about 2.5 times that of the odds of White men in each decade. Hispanic men’s odds of being in a first marriage with a much-older wife versus one of the same age were also twice the odds of White men in 1980 and 2010-14. Analyses demonstrated that marital age gaps have, indeed, changed significantly since the second-wave women’s movement, and that while age homogamy increased, the odds of being age heterogamous also shifted for people with different characteristics. / Sociology