If you are cooking a recipe and you want to stay as close to period with it as possible what do you do about salad oil?
For recipes such as most corn bread ones, I simply use 2/3 as much melted lard or one can use melted butter in the same amount as called for salad oil.
Also olive oil was used in salads, making mayo and other things where only oil will do. It is listed in most lists of groceries as sweet oil. There was some production of olive oil in California, but much of it came from Italy and Spain, just as much of it does today.
Also melted bacon grease was mixed with vinegar and poured hot over salad greens, making the "Wilted Lettuce Salad" popular at the time.