The steak or chicken salad, topped with french fries and shredded cheese, was invented at Jerry's Curb Service in Bridgewater, PA (next door to Rochester, PA, as indicated elsewhere in this thread and just up the road from Pittsburgh). It is one of the few remaining car-service restaurants around -- pull your car in (the older/hotter/faster the better) and a car hop will be right out to take your order. Jerry's was demolished and rebuilt in true retro style a few years ago and still serves great burgers, fries, Dorsey's and those world-famous steak salads. Google Jerry's Curb Service and you'll find their website (now selling franchises!) and this ditty about how it all began:
It was on a fateful night in the early 1960's that the now famous Steak Salad was born. A customer placed a rather unusual order - a steak sandwich, hold the bun, add fries and salad dressing. Not one to disappoint a customer, Donna Reed placed the order. She noticed the man cut up the steak, mixed in the fries and poured the salad dressing on top. Curious about this rather odd concoction, Donna decided to try it for herself, but with one small change. Donna placed her sliced steak, fries and salad dressing atop a fresh bed of lettuce. Creating what is now a staple in the restaurant industry - the Steak Salad!
In honor of that nameless customer who inspired Donna to create the classic Steak Salad, Jerry's Curb Service still offers the original order - sliced steak and hand cut fries with a side of salad dressing.