BoxRec

The Jr. Welterweight title was vacant when Barney Ross gave up the title in 1935 and stayed that way until 1946. Then Tippy Larkin won the vacant title against Willie Joyce, beat Joyce in a rematch in 1946,and then the title was vacant again until 1959.
So, (except for a brief period) the Jr. Welterweight title didn't exist for almost 24 years from 1935-1959.

What is most likely to have happened if the best fighters at this weight would have been competing for the Jr. Welterweight title?

Perhaps Tony Canzoneri would have won it back and had it in the late 1930's. Maybe Henry Armstrong would have had it for a couple of years. Beau Jack could have been champion in the early 1940's as well.

Perhaps some fighter who never win a world title would have won the Jr. Welterweight title at some point. Maybe Juan Zurita or Art Aragon.

Any educated guesses on what might have happened with the Jr. Welterweight title during this time?

Bummy Davis may have been a player.He never won a title.Maybe this coulda been gold for him.
In 1944 he weighed 142 and a half and stretched Bob Montgomery in one round.
Bummy could really bang.

I think the prevailing factor here would be incentive. You could end up with a less than great champion, or you get entice a LW moving up to face a guy just a little small for WW.

This is worthy of more consideration. So called purists may disagree, but I believe unequivocally that the JWW division has been great for boxing.

Some time between 1936 and 1940, Lou Ambers would have won a title belt, if the division was around.

Armstrong almost for sure, 99.9% sure, would've had it at least at some point.

Hard to say who else. Ambers very possibly, maybe Sammy Angott. Any top quality lightweight or small-ish welterweight would've at least been a contender for it.

Yeah, it would have been interesting. There were so many good fighters around at this size at in the 1930's and 1940's. Hard to say about the 1950's.

No doubt some great lightweight and welterweight champs would won the Jr Welterweight title as well. However, there probably would have been some guys who never won the the lightweight or welterweight title who would have won the Jr Welterweight tile and been a world champion had the title existed.

I just thought it was strange and unfortunate that title was abandoned in this weight class for so long.