Americans continued to abandon the nation's heartland over the past decade, moving into metropolitan areas that have grown less white and less segregated, the 2010 Census showed.

The U.S. population grew by 27 million over the decade, to 308 million. But growth was unevenly distributed. Metropolitan areas, defined as the collection of small cities and suburbs that surround an urban core with at least 50,000 people, accounted for most of the gain, growing 10.8% over the decade to 257.7 million people.

Rural...