JF Ptak Science Books LLC Post 344
This was a remarkable photograph for the information it presented when it was published in The Illustrated London News on 30 July 1921. That's a real sea of humanity surrounding the canvas ring, and probably the largest crowd ever assembled in Jersey City.
The image was made by a photographer for The New York Times from an airplane about 2,000 feet over the arena.
The fight between the two men was billed as "The Fight of the Century", and it was, up until that time. It was probably the event that was most-listened to than any other event in history, the early radio broadcast of the fight reaching at least 300,000. But since there were so many mass venues listening to the fight--or watching its progress via displayed messages transcribed from the radio broadcast--it is really pretty impossible to say how many followed the event on that day.
(The image below shows a very large crowd of approximately 10,000 in Times Square waiting for the returns f the fight.)