In just about a month, the U.S. Census Bureau's population clock for the United States will indicate that the estimated U.S. population has crossed the 300 million mark. As the world's third largest country, the U.S. continues to grow, netting one new resident approximately every ten seconds. In anticipation of the big day, the Census Bureau provides a nice comparison of the populations in 2006 (300 million), 1967 (200 million), and 1915 (100 million).