Via the IMF
The visualization shows us the age distribution of the US population from 1933 to 2100. Until 2010, the data is the observed and recorded demographic information, and from then until 2100 forecasts are used. These are taken from the Human Fertility and Human Mortality Databases.
On the left you can see the male population, while on the right is the female. Post 2010, the blue and red areas reflect the uncertainty ranges in these projections.
Source: Stephen Holzman