So just where are the Ozarks, exactly? Glad you asked.
There is a basic geographic boundary, though I’ve seen it argued on paper some, and it isn’t as definite in some places as it is in others.
The region is roughly triangular and transcends the borders of Missouri, Arkansas, Oklahoma, and even Kansas.
To give a very general description, the Ozark boundaries are basically the following: From just west of the junction of the White River and Black River in the southeast part of the region (Arkansas), go northeast to the Mississippi at Cape Girardeau (Missouri), then northwest to a little above the Missouri River at St. Charles County (Missouri), then continue west above the Missouri River to the Howard/Saline County line (Missouri), then southwest to the Kansas side of the Spring River on the Kansas/Oklahoma line (Kansas), then follow the Neosho River, and then Grand River, southwest to about Muskogee (Oklahoma), then go due east above the Arkansas River Valley (Arkansas) and back to where we started just west of the White River/Black River intersection (Arkansas).
I realize that description may be hard to follow, and you really need to see a map to get the picture. I’ve included one or two here. Also, please keep in mind that the description is very broad. Again, see the map.
Who decided the borders? Beats me. Geographers did at some point, but when or who I really can’t say. I’ll admit, I was a little surprised at how far the Ozarks extend when I first saw a boundary map a few years ago.