America's population is always changing, and it develops in different ways in different parts of the country.
The US Census Bureau recently released its estimates of how the populations of America's counties and cities changed between July 1, 2013 and July 1, 2014.
This map shows the overall rate of population change in each county over that year. The then-booming oil-rich counties of Texas and western North Dakota drew a huge number of people in. Most of California and the big cities of the Sunbelt also continued their long term growth trends:
Business Insider/Andy Kiersz, data from US Census Bureau
Here are the fifteen fastest growing counties in the country. Nine of them are in North Dakota or Texas:
Business Insider/Andy Kiersz, data from US Census Bureau
And on the other side of the coin, here are the fifteen counties that saw the biggest drops in population between 2013 and 2014:
Business Insider/Andy Kiersz, data from US Census Bureau