This study documents the changing racial and ethnic mix of America's children. Specifically, we focus on the unusually rapid shifts in the composition and changing spatial distribution of America's young people between 2000 and 2008. Minorities grew to 43 percent of all children and youth, up from 38.5 percent only eight years earlier. In 1990, this figure stood at 33 percent. Among 0–4-year-olds, 47 percent of all children were minority in 2008. Changes in racial and ethnic composition are driven by two powerful demographic forces. The first is the rapid increase since 2000 in the number of minority children—with Hispanics accounting for 80 percent of the growth. The second is the absolute decline in the number of non-Hispanic white children and youth. The growth of minority children and racial diversity is distributed unevenly over geographical space. Over 500 (or roughly 1 in 6) counties now have majority-minority youth populations. Broad geographic areas of America nevertheless remain mono-racial, where only small shares of minorities live.