The breaded tenderloin is NOT limited to Indiana. It is a very very common sandwich in Iowa. It’s almost as prevalent as a burger.
My 98 year old mother would invariably order one if it was on the menu. I find myself ordering them quite often these days as well.
Most restaurants also now offer an un-breaded version.
I think anywhere you had German farmers raising hogs, you have tenderloins. Sorta like Schnitzel but better :-)
Breaded tenderloins are definitely an Iowa favorite, as they should be given the number of hogs in Iowa. A favorite at the Culver’s chain. Ted’s Coney Island around Des Moines make a great one.
And Iowa is home to the original ‘loose meat’ sandwich, the Maid-Rite, which has seen declining popularity.