History. The hamburger is actually a far more recent invention than most realize. While countless culinary innovators take credit for creating the burger, perhaps the most likely candidate was New Haven, Connecticut lunch-cart operator Louis Lassen. As the story goes, in 1900, Lassen served a ground beef sandwich to a worker on the go, giving rise to the hamburger. The Lassen family is continuing the tradition 113 years later. At Louis’ Lunch, the burgers are cooked in vertical cast-iron gas stoves and served on plain bread; the only condiments available are cheese spread, tomatoes, and onions. Ingredients such as ketchup, mustard, and mayonnaise are strictly forbidden. According to the owners, students from nearby Yale University are often caught trying to smuggle ketchup into the grill. They are politely asked to leave.