I was watching a Vikings vs Giants game and there were brief images of a stadium from the 1960s. In the image, the goalposts looked different - they looked more like shorter, squatter rugby goalposts, not nearly as tall as their current form. They looked something like this or this. By the 1980s, it looks like they took their current form, as evidenced from the field in Super Bowl XVI. When and why did the goalposts change their shape?
The posts in your 2nd image reflect the rugby football roots of american football.
In 1927 they were moved to the back of the end zone which had been introduced in 1912, due to them interfering with play and movement in the end zone.
You can see in your first image where this is happening, even though they don't have an end zone marked out.
The NFL moved them back up to the goal line in 1933, and then back to the end line in 1974.
Your first image is within this era, 1963.
