writes "The United States' population will hit 300 million on Tuesday morning, just 39 years after it reached 200 million, the US Census Bureau estimates. A 'population clock' will record the milestone at 0746 (1146 GMT) — a timing based on calculations that factor birth and death rates and migration."
From the article: "But it is not possible to say if the 300-millionth American was a new-born or crossed one of the US borders. Correspondents say that there is not expected to be the same hullabaloo as when the figure of 100 million was reached in 1915, or the double century in 1967 when President Johnson gave a speech and newborn Robert Ken Woo Jr was hailed the 200-millionth American by Life magazine. Today, the population figure is mired in the divisive politics of immigration — a hot-button issue ahead of the 7 November mid-term elections, they say."
The story has lots of interesting stats and graphs, for those of us so inclined.