Answer:
The US population in 1950 was 152.3 million (it is currently estimated at around 328 million).
The population pyramid of the US in 1950 looked almost as a perfect pyramid. The median age was lower than 30 years old, meaning that the population was relatively young.
As a result, the lowest-age brackets in the pyramid are the most populous, and the oldest-age brackets of the pyramid are the least populous.
I have uploaded a small image of the 1950 US population pyramid.