Mostly-free market capitalism with rules and ethics in place to prevent things from getting out of hand, like bans on slavery/sharecropping, fair child labor laws, unions in place for unskilled workers and government bodies to keep unions from getting too corrupt, bans on scrips (paying workers in bullshit certificates they can only use at the company store, this shit was everywhere in the 1800s, you have to pay them in actual cash, damn it!), and bans or restrictions on unfair business practices (so you can't just buy every damn oil well in the country so none of your competitors have any supply like fucking Rockefeller did)
Shit was corrupt as hell back in the day, tons of people just looking for ways to not pay their workers. you have to have SOME kind of rules in place or else you get shit like child slave coalminers dying of black lung disease at age 19 because they'd been coal mining since they could hold a shovel in ridiculously unsafe conditions with zero safety measures, and he couldn't have even moved somewhere else because he was 20,000$ in debt to the company store since the rent on his company-approved housing was slightly more than his monthly wage.
And don't get me started on "waste" coal, where they wouldn't pay you for the day because you didn't correctly guess the weight of your mine cart (this actually happened, if your haul weighed too much or too little they wouldn't pay you but keep the coal you brought up anyway)