No, it's a product of violent riots and union action where thousands of workers died at the hands of police and hired guns.

I don't quite see this adding up to "thousands" i.e. more than 1999 people, even if you double it for not being an exhaustive list: https://en.wikipedia.org/wiki/List_of_worker_deaths_in_Unite...

Correct, I meant to say where thousands of workers mobilized, some of which died or were injured.

In the Law, yes, the Fair Labor act was enacted during his presidency. But the Idea of 8 hours of work, 8 hours of sleep, 8 hours for what you will long predates him, and 8 hours was already a standard shift at some (many?) factories by that time.