In the middle of the twentieth century, the Bureau of the Budget, in conjunction with the Census Bureau and other federal statistical agencies, introduced a widely used unit of statistical geography, the county-based Standard Metropolitan Area. Metropolitan definitions since then have been generally regarded as comparable, but methodological changes have resulted in comparability issues, particularly among the largest and most complex metro areas. With the 2000 census came an effort to simplify the rules for defining metro areas. This study attempts to gather all available historical geographic and commuting data to apply the current rules for defining metro areas to create comparable statistical geography covering the period from 1940 to 2020. The changes that accompanied the 2000 census also brought a new category, "Micropolitan Statistical Areas," which established a metro hierarchy. This research expands on this approach, using a more elaborate hierarchy based on the size of urban cores. The areas as delineated in this paper provide a consistent set of statistical geography that can be used in a wide variety of applications.