The "least disputed" inventor of the hamburger is Louis Lassen, who began selling them in 1900 at his lunch stand in New Haven, Conn. Beef patties comprised of five cuts of meat are layered with sliced onion, then broiled in the restaurant’s historic vertical presses that date to 1898. Served simply between toasted white bread with a sharp cheddar spread and a slice of tomato, the explosion of beefy goodness on first bite is a profound hamburger experience not to be missed.