How many Americans are over the age of 18?

According to the US Census Bureau, the population of the USA in 2006 was 299, 398, 484. Of that population figure, 24.6% were under the age of 18. Therefore, the population of the USA over the age of 18 is: 225,746,457

For more information, see: http://quickfacts.census.gov/qfd/states/00000.html

-Steve Reid