Rarely has Hollywood produced a character as stubborn and cussed as Newton Knight, the hoary hero of "Free State of Jones", the American Civil War epic starring Oscar-winning Matthew McConaughey.

Unlike such memorable screen curmudgeons as John Wayne's Rooster Cogburn in "True Grit", Newt Knight actually existed, and was, if anything, more dogged in real life.

Knight's story turns the accepted history of the American South on its head, according to the film's director Gary Ross, best known for "The Hunger Games", "Seabiscuit" and "Pleasantville".

A poor Mississippi farmer who had fought with the Confederate army, Knight deserted to lead a two-year revolt against the Rebels that history books have for the most part glossed over.

Knight's anger was first sparked by the way rich slave owners were exempted from conscription.

It was further inflamed by Confederate taxes that robbed the poor of what little they had. So he and his comrades united with runaway slaves in the swamps to launch a guerilla war against the plantation owners.

Knight and his mixed army of blacks and whites carved out their own free state, declaring their loyalty to the Union and running up the Stars and Stripes after capturing the capital of Jones County and taking a large swathe of the southeast of the state.  

- 'Hidden history' -

Ross said it was no surprise many Southerners still find it hard to accept Knight. 

"Matthew McConaughey and I put a lot on the line to correct a lot of history that was wrong, that had been mistold, rewritten and forgotten," Ross told AFP.

"I am very proud how the film corrects what 'Gone With The Wind' and 'Birth Of A Nation' got wrong," he said -- referring to the two classic US films -- despite the $50-million movie's relatively poor showing at the US box office.

Ross admitted some audiences might have found the idea of such a rebellion in Mississippi incredible, given that it was the most "Southern" of the Confederate states which would later became notorious for its Ku Klux Klan lynchings.

"But it did happen. We stayed very close to the facts," Ross said.

"Many people received the film with open arms. But some others had difficulties embracing the coalitions (of blacks and poor whites) that we described."

- Teetotal sharpshooter -

To further confound stereotypes, Knight -- a teetotalling "primitive Baptist" libertarian who never cursed but was a crack shot -- took up the cause of freed slaves after the Civil War.

He married a black woman, proudly recognising his mixed-race children. 

"Americans have been sold a happy ending to the Civil War," Ross added. "The slaves were freed, all our problems were solved.

"But that's not true. No sooner were those slaves freed than they were re-enslaved. And that is just not a thing that everybody wants to know about."

McConaughey won the 2014 Oscar for best actor for his role in the "Dallas Buyer's Club". His performance as Knight has also been widely praised, but he admitted that for some it was a "hard pill to swallow".

"It is heavy, man. It's an action movie but it is not the type of film you can have a conversation in and then go out in the middle to get some popcorn. 

"It's a real you lock down go for the ride, wow, wow, wow kind of film," he said, speaking, as Ross did, via video link from New York.

"I think it has a huge relevance to the culture and politics of our nation at this time," something McConaughey thinks audiences outside America might see more clearly. 

"I see it as a great quiver to have in our arsenal. I see it also as a feather in my cap that will be come to be seen more so as time goes on."

Ross, who began writing the script long before the success of "12 Years a Slave", said he was convinced that "in five years or 10 years" people will still be debating the film "because it surprises, provokes and challenges us".

"I am just glad it is out there on a shelf and in the ether. I am intensely proud of it. It and 'Pleasantville' are my best films."