Never been to the Ozarks myself but big black cats are something I find really interesting. We get the same sort of reports over here in Gloucestershire, people spotting large black cats in the fields and along the edges of woodland. Nobody ever believes you when you say it but there's just too many sightings for it all to be misidentification or whatever the sceptics call it.
Three times in one month is significant though mate, thats not a coincidence. Makes you wonder if its territorial, like it has a regular route it walks.
Have you managed to get any photos or found any prints? That would be massive. Would love to hear more details about where exactly and what time of day you spotted it.