Thousand Island dressing is a creamy salad dressing and condiment made from a base of mayonnaise and usually ketchup or tomato purée and chopped pickles, and typically including a variety of other ingredients. It was initially popularized in the Thousand Islands region of the upper Saint Lawrence River spanning New York and Canada. Historically a salad dressing, it has been widely adopted by fast food chains as a "special" or "secret" sauce of their own variation based on the Thousand Island recipe.