Mushroom Scalloped Potatoes

1 can cream of mushroom soup
1/2 c. grated American cheese
4 c. sliced potatoes
1 tsp. salt
2/3 c. evaporated milk
1/4 c. onion, chopped fine
1/4 c. grated American cheese

Combine soup, 1/2 cup cheese, onion, salt and milk. Add potatoes. Mix and put in a greased baking dish. Top with 1/4 cup cheese. Bake at 350° until potatoes are tender, about 1 hour and 15 minutes.