Complex sentence: By 1955, Marzetti's dressings had become so renowned that the upstairs kitchen of the restaurant became a full-scale factory and the Marzetti brand of salad dressings found its way into grocery stores throughout Ohio.
Split into simpler sentences: By 1955, the dressings had become so renowned that the upstairs kitchen of the restaurant became a full-scale factory. Thus the Marzetti brand of salad dressings found its way into grocery stores throughout Ohio.