Year in and year out, we dutifully track every little change in the size and composition of the U.S. population — so forgive us if we get a little more excited than most about a major numerical milestone: the Census Bureau estimates that on October 17, 2006, the nation’s population hit 300 million for the first time, up from 200 million in 1967 and 100 million in 1915... and fewer than 40 million in 1868, when the first World Almanac was published. For a little perspective on how the rest of the nation has changed, the Census Bureau offers some fascinating comparisons of key statistics (the price of milk, the median age of the population, and more) at the 100, 200, and 300 million markers.

–C. Alan Joyce