Growth of human capital (change in the fraction of a metro area's college-educated labor force) is typically seen as generating desirable outcomes (e.g., economic growth). With a sample of >200 U.S. metro areas for 1980, 1990, and 2000, the author explores why some economies have more human capital than others and finds two significant correlates: population and the existing stock of college-educated labor. If population and human capital growth are positively associated with education, these results suggest that larger, more-educated metro areas should have the fastest rates of growth. The evidence supports this conclusion.