Louis' Lunch is a restaurant in New Haven, Connecticut. It is considered the birthplace of the hamburger. Although this is contested, but it is hard to prove one way or another. It is known for serving hamburgers on toast with only cheese and tomatoes. It is also known for a lack of condiments (mustard, ketchup, mayo etc.) since they feel they interfere with the taste. They serve their burgers with potato chips, although potato salad was added to the menu later. Unlike most burger chains, the burgers are made with ground sirloin cooked medium rare to medium, and instead of cheese slices, the burgers can be topped with a cheese spread, as well as onions and tomatoes, but these are the only toppings.
Louis' Lunch is the oldest hamburger diner existing in the United States, and one of the first to sell steak sandwiches. They have lingo in which food is to be ordered, and do not accept credit cards.