I suppose the mill you reference is War Eagle Mill. It's interesting to visit. I don't know about the caves. I live up the mountain from Devil's Den State Park, and they have closed many caves in AR due to a fungus that the bats get, and they're afraid of us spreading it.
If you're going interstate, there's a Cabela's at exit 82 Rogers. Stop to see Fort Smith Historic Site--frontier justice court covering the Indian territory. Nite Lite Outdoors, Clarksville--dogger gear.
Backroads: Out of 'Sprangdale' 412 Hwy to Huntsville, home of Orvil Faubus, Granny's Kitchen for dinner (that's the Southern midday meal). Madison Co. is 'Booger County' in AR, though I believe MO gives your Douglas County that honor. Pig Trail 23 out of Huntsville, though a lane is closed due to washout over the mountain.
If you really want some backroads, connect with 74 in Huntsville to Kingston, then down 21 through Lost Valley/Boxley on down to I-40. Lots of hillbilly history around there, and you may see some Elk.
Have a good time.