We highlight the paradoxical implications of decadal reclassification of U.S. counties (and America’s population) from nonmetropolitan to metropolitan status between 1960 and 2017. Using data from the U.S. Census Bureau, we show that the reclassification of U.S. counties has been a significant engine of metropolitan growth and nonmetropolitan decline. Over the study period, 753—or nearly 25% of all nonmetropolitan counties—were redefined by the Office of Management and Budget (OMB) as metropolitan, shifting nearly 70 million residents from nonmetropolitan to metropolitan America by 2017. All the growth since 1970 in the metropolitan share of the U.S. population came from reclassification rather than endogenous growth in existing metropolitan areas. Reclassification of nonmetropolitan counties also had implications for drawing appropriate inferences about rural poverty, population aging, education, and economic growth. The paradox is that these many nonmetropolitan “winners”—those experiencing population and economic growth—have, over successive decades, left behind many nonmetropolitan counties with limited prospects for growth. Our study provides cautionary lessons regarding the commonplace narrative of widespread rural decline and economic malaise but also highlights the interdependent demographic fates of metropolitan and nonmetropolitan counties.