There is a colorful website for the town of Matewan (with current info on the Hatfield/McCoy reunion!) with a link to an article on what they call the Battle of Matewan:
http://www.matewan.com/History/battle2.htm
As to the question of whether the Sayle's film is 'historically accurate' I would say yes, it is an historically accurate fictional story of the mine wars in West Virginia in the early 20s.
Of course, if you believe any historical fiction can't paint as accurate a picture as historical non-fiction can, which some people actually do believe, then you wouldn't find it to be accurate no matter what sources get cited.