Many of the areas that experienced the most rapid growth from July 2011 to July 2012 are located in or near the Great Plains and West Texas, according to U.S. Census Bureau estimates released on Thursday. Midland, Texas, for instance, was the fastest-growing metro area with a 4.6 percent increase. For micro areas — an urban cluster of 10,000 to 49,999 residents — Williston, N.D., had the highest growth rate of 9.3 percent. At the county level, Williams, N.D.; Geary, Kan.; Richland, Mont.; and Stark, N.D.; made the list of the five fastest-growing counties with at least 10,000 residents.

"There are many factors fueling this growth on the prairie, but no doubt the energy boom is playing a role," said Thomas Mesenbourg, a Census Bureau senior advisor. He pointed out that the Permian Basin located in West Texas and North Dakota accounted for nearly half of the U.S. growth in firms that mine or extract oil and gas.

In general, the South and West experienced the highest growth rates with increases of 1.1 and 1.04 percent, respectively, compared to 0.3 percent in the Northeast and 0.25 percent in the Midwest. Forty of the 50 fastest-growing areas were located in the South or West; half of the top micro areas were located in the South and 14 in the West.

According to an Associated Press story, 1,135 counties had more deaths than births, up from 880 counties in 2009. Chattahoochee, Ga., where Fort Benning is located, was the fastest-growing county with at least 10,000 residents at 10.1 percent. Texas had 11 of the 50 most rapidly growing counties; Florida, meanwhile, had the first and second fastest-declining counties in terms of population, followed by two in Alabama.

Several major cities passed milestone marks, including Philadelphia at 6 million with a 0.4 percent increase and Las Vegas at 2 million residents with a 1.7 percent increase. Fifty-two metro areas now have at least 1 million residents, and nine metro areas have at least 5 million residents. Overall, the population increased 0.75 percent compared to 0.73 percent in 2011.