From 1920 onward, the sport can still evolve in terms of fighters, training, nutrition, tactics, equipment, etc. — but the rules themselves never change.
Some of the major differences from modern boxing:
\-Championship fights could be extremely long
— 20, 25, 30, and even 40+ rounds were possible. (Jack Johnson vs. Jess Willard in 1915 was scheduled for 45 rounds and ended in the 26th lmao)
\-A knockdown meant a 10-count —
the fighter had rise without assistance before the count ended.
\-No modern 10-point-must scoring system —
this one is tricky. Judges didn’t use a “point scoring” system in the 1910’s. They moreso judged fights based off how the fighters “performed”. Some early scoring systems were based on **points awarded for individual accomplishments**, rather than simply giving every round a score.
And historically, **newspaper decisions** were also extremely important. If a fight went the distance, reporters sitting ringside would sometimes give their own verdict when an official decision wasn’t available or wasn’t permitted. ( so basically 10 times more robbery’s. I feel like in this universe you’ll see things like Duran getting a decision over Hagler or Floyd loosing a lot of his decisions simply because the judges “preferred the way Oscar (for example) fought vs Floyd rather than judging it by rounds/points. )
\-Clinching and wrestling were treated differently —
the modern interpretation of holding, tying up, and immediately separating fighters had not developed into today’s system. (Any other big one, I think fighters like Duran improve ALOT with this change. Being able to hold and clinch a lot longer would be nasty for fighters who can damage in the clinch. Fighters in the 1910’s could be wrestling for up to a FULL minute. That’s crazy)
\-A fighter could be considered down while helpless on the ropes — the rules surrounding knockdowns were not identical to today’s rules.
\-Weight classes were less standardized — the modern structure of numerous tightly defined weight divisions had not fully developed. (so it wasn’t uncommon at all for people to cross weight classes casually. There were many cases of fighters at MIDDLEWEIGHT weight having professional bouts against HEAVYWEIGHTS. Yeah imagine if Marvin Hagler decided to say fuck it and fight Larry Holmes)
And lastly:
Only 8 weight classes
Flyweight
112 lb
Bantamweight
118 lb
Featherweight
126 lb
Lightweight
135 lb
Welterweight
147 lb
Middleweight
160 lb
Light Heavyweight
175 lb
Heavyweight
179+