The 2010 Census kicked off in Noorvik, Alaska, with the Census Bureau conducting in-person counts. The U.S. Constitution requires a formal count of everyone living in the United States every 10 years to determine how many seats each state will get in the House of Representatives. Census data is also used to help determine how to distribute more than $400 billion in federal money each year and to draw state and local legislative district lines.
The final tally put the U.S. population at 308,745,538, an increase of about 9.7 percent from 2000. Results found that Nevada had the biggest growth in population, while Michigan had the biggest drop in population. For more details on a given state or county, check out this interactive map from the U.S. Census Bureau. Simply rolling your mouse over a state gives you its total population, and how it's changed every decade since 1960. The map also provides figures on a state's population by race. Click on a state to get county-by-county info. This interactive map from The New York Times goes a step further, providing each county's population by race.