We hit a low point of 2.3 million births in 1933 (following the Great Depression). The babies born during that year are turning 93 this year. The numbers gradually increased after that reaching almost 2.6 million in 1940 and just above or below 2.9 million during the years between 1942 and 1945, babies who are 81 to 84 today.
Then things took off with the number of babies reaching 3.4 million in 1946, the onset of the baby boom, over 4 million by 1954 and a peak of 4.3 million in 1957. They stayed above the 4 million mark through 1964, the last year of the baby boom.
The chart below shows the annual number of births each year in orange (and the birth rate in blue).

The 85+ group will grow by 44% this decade and will skyrocket by 58% during the 2030’s, before slowing to a more moderate 29% growth rate in the 2040’s.
The number of Americans aged 65 to 84 is only projected to grow 21.5% this decade and then essentially stop growing after 2030.

Source: Harry Margolis