Abstract: This dissertation is part of a larger project that investigates the causes and consequences of trends in educational assortative mating in the United States. Past research has shown strong evidence of increases in the educational resemblance of spouses in the United States since at least the 1960s, which has led to concern that marriage patterns may contribute to growing economic inequality. This dissertation consists of four separate but related papers that contribute to our understanding of these trends, their demographic sources, and their potential consequences. Despite growing interest in assortative mating over the past decade, research on trends since the early 1990s is limited. Chapter 2 describes trends in the educational resemblance of spouses in the U.S. between 1940 and 2003. I find that the odds of educational homogamy are higher today than in any other decade since 1940, although there is evidence of a possible slowing of these trends since 1990. My analysis shows that these increases were generated by different portions of the education distribution in different periods. Chapter 3 examines the impact of first marriage, remarriage, marital dissolution, and post-marital educational upgrading on the educational resemblance of spouses. I find that the vast majority of age variation in the educational resemblance of spouses is attributable to assortative mating into first marriages - other demographic factors have relatively small and offsetting effects. In Chapter 4, I examine transitions into and out of cohabitation and marriage, and find little evidence that cohabitation 'weeds out' educationally dissimilar couples prior to marriage. Finally, many studies of educational assortative mating are justified, at least in part, by the potential effects of assortative mating on economic inequality, but very little is known about this relationship. As a first step toward understanding the impact of increased spousal educational resemblance on inequality, Chapter 5 examines the contribution of changes in the association between spouses' earnings to increases in earnings inequality among married couples since the late 1960s. I find that about 30% of the increase in earnings inequality among married couples can be attributed to changes in the association between spouses' earnings.