Every year, except in the year after a decennial census is conducted, the Census Bureau releases population estimates for the nation’s more than 3,000 counties and equivalents, along with Puerto Rico’s municipios. Yesterday, we published the first such estimates since the 2010 Census and they show us the first measure of how much each county has grown since Census Day ─ April 1, 2010.

These estimates pertain to July 1, 2011, and provide evidence that different patterns of growth are emerging than what we witnessed during the last decade.

Traditionally, when we think of people packing up their belongings and moving out of state, we often picture them seeking out the sun and surf of Florida.

If we look at the counties with the highest rates of growth during the 15 months after the 2010 Census, we see that several in the top 10 were located far outside what many would consider the Sun Belt, including one in North Dakota, one in Iowa, and one in Washington state. Two more are in the New Orleans vicinity, providing further evidence that this area continues to rebound from 2005’s Hurricane Katrina.

Expanding the list out to the top 50 shows a more traditional pattern, with 38 of the fastest-growing counties over the period located in the South. That said, three of the top 50 are in North Dakota, which had one of the slower rates of growth among all states between the 2000 and 2010 censuses. That gave North Dakota more counties in the top 50 than Florida (which had only one), as many as North Carolina, and more than every state except for Texas, Georgia and Virginia. Furthermore, another two counties are in neighboring South Dakota.

The counties among the 10 with the highest numeric growth are exclusively in the Sun Belt, however, with four each in Texas and Southern California, and the remaining two in Arizona and Florida, respectively. Harris, Texas, home to Houston, led the way, gaining more than 88,000 residents over the period.

These estimates are the first for counties based on the 2010 Census. The Census Bureau uses births, deaths, administrative records and survey data to develop them. Released along with the county numbers were comparable estimates for metropolitan and micropolitan areas. In the coming months, we will publish estimates of the total population of incorporated places, as well as national, state and county population estimates by age, sex, race and Hispanic origin.