The recent increase in American divorce rates has aroused a great deal of media publicity, popular discussion, and social science research. Several recent works have begun to reexamine the origins, trends, and implications of divorce in American history. This paper presents systematic data concerning the extent of divorce in three North Central states for the 1810–60 period. The findings establish the incidence of mass divorce for a considerable period prior to official divorce statistics. Major patterns are analyzed and compared to late 19th-century data from the first governmental studies of divorce for the 1870–1900 decades. While some urban-rural differences are found, changing laws and norms played the principal role in the increase in divorce rates during the 1800s. The final part of the paper discusses the implications of these findings for understanding marital disruption in social-historical perspective.