Hidden in plain sight on East Main Street in Troy, Ohio, K’s Hamburger Shop serves up biscuits and gravy so transcendent, you’ll find yourself plotting return trips before you’ve even paid your bill.

Mehlman’s Cafeteria sits in Clairsville, right off Interstate 70 in eastern Ohio, looking exactly like what it is: an honest-to-goodness cafeteria that doesn’t need to pretend to be anything else. No ...