Globally, the number of multiracial people is exploding. In 10 US states, the percentage of multiracial residents who are of school age--between 5 and 17--is at least 25 percent. In California alone, it is estimated that 15 percent of all births are multiracial or multiethnic. Despite these numbers, mixed-race people have long struggled for a distinct place on the identity map. It was only as recently as 2000 that the U.S. Census Bureau began to allow...