High birth rates among Hispanics--now the largest minority group in the country--and the continued influx of immigrants boosted the American population by 2.8 million to 290.8 million in 2003, according to the U.S. Census Bureau. If that pace keeps up, predicts John Haaga of the Population Reference Bureau, there could be 300 million people living in the United States within the next four years.

The nation's southern and western regions welcomed the most new residents, with Nevada adding more people than anywhere else in the country, due in part to a combination of climate, recreation, and more affordable housing, observes Brookings Institution demographer William Frey. In fact, Nevada has been the fastest-growing state for 17 years now.

The South now accounts for 36 percent of the nation's total population, with the West comprising 23 percent, the Midwest 22 percent and the Northeast 19 percent. California, Texas, and Florida, the three fastest-growing states (see chart), combined account for 42 percent of the nation's population increase between July 2002 and July 2003. States that moved into the top 10 this year were Delaware, California, and Hawaii.