New Haven, Connecticut
This roadside luncheonette now in its fourth generation of family ownership is reportedly ground zero for the American hamburger, at least according to some. The legend goes that in 1900, a hurried diner asked for something he could eat on the run, and original proprietor Louis Lassen accommodated him with the ground excess from his usual steak sandwiches between two pieces of toast, and voila — culinary history was made. A hamburger ground and molded onsite is still the signature here almost 120 years later, but don't hope for any condiments: It's restaurant policy not to let anything but cheese, tomato, and onion distract from the simple pleasure of a patty grilled to perfection.
Related: From Mongols to McDonald's: The History of the Humble Hamburger