I’ve heard that, too.
This map is very interesting, in terms of where they are (such as punctuating ferquently the great empty spaces of Nevada and Utah) and where they aren’t (such as a the inland “MIssissippi Delta” and a strange slash from Virginia (the Shenendoah Valley?) across Pennsylvania, and up the Eastern edge of New York).
>> “MIssissippi Delta” and a strange slash from Virginia (the Shenendoah Valley?) <<
Good observation about a couple of famous agricultural areas!
Also striking is the crescent sweeping from mid-Alabama up thru northeastern Mississippi, all the way to the Tennessee line. It’s an old cotton-producing area that was a stronghold of the slave-holding plantation aristocracy before the Civil War.
This latter region is often called the “Black Belt” in Alabama (mainly for its rich soil, but also for its black-majority population) and the “Prairie” in northeastern Mississippi. Fascinating how such land-using and demographic patterns have been maintained over nearly 200 years!
A good part of that “strange slash” in PA is valley farmland.