In January 2007, the United States had a population of approximately 299.89 million. Between January and February of that year, the population increased to 300 million. By the end of 2007, the United States had a population of approximately 302.53 million.
These figures are only estimates, as the U.S. Census Bureau only conducts the census every 10 years. The Bureau conducted the most recent censuses in 2010 and 2000. At the time of the 2000 census, the United States had an exact population of 281,421,906. By the time of the 2010 census, the U.S. population had grown to 308,745,538.
As of October 2015, the most recent estimates place the U.S. population at approximately 321.86 million.