The majority (84 percent) of the 17 million children of immigrants in the United States live in the 100 largest metropolitan areas. Children of immigrants drove the growth in the child population under age 18 nationally and in the largest metros: if it was not for them, the child population in the top 100 metros overall and in many metros would have declined in the last decade. Driven by immigration and population momentum, the child minority share across the top 100 metros reached 51 percent in 2009 and many of the largest metros became "majority minority" metros.