It goes back to the ‘Height of Buildings Act’ of 1910. In recent years, they have been trying to make exceptions for areas outside of the original L’Enfant plan; but I hope they never allow DC to be made a ‘skyscraper’ city. (I don’t go down to the District much anymore, but when I worked there it was fun to to try and understand how the height of a building related to the width of the street it was on):
https://en.wikipedia.org/wiki/Height_of_Buildings_Act_of_1910
Thanks for the info.
It makes sense from a security standpoint when they knew aircraft would be common overhead soon.