The Reuben is an American deli sandwich of corned beef, sauerkraut, Swiss cheese, and Russian or Thousand Island dressing, grilled between slices of rye bread. Its origin is disputed: it's most often credited to Omaha grocer Reuben Kulakofsky in the 1920s, with a competing claim crediting New York deli owner Arnold Reuben in the 1930s. Common variations swap pastrami for the corned beef, use Russian dressing instead of Thousand Island, or substitute a vegetarian filling such as grilled portobello mushroom. It's a Midwest and Northeast deli staple, usually served with coleslaw, potato salad, or pickles.