According to Official Guinness Records,
Loran Green and Friends of Hi Line Promotions made a burger of pure Montana beef weighing 2.74 tonnes (6,040 lb) at the Sleeping Buffalo Resort at Saco, Montana on 5 September 1999.The hamburger measured 7.32 m (24 ft) in diameter.A crowd of more than 3,500 people gathered to watch the burger cook for about two hours on a specially made 576-square-foot grill. The burger would have cost more than US$7,000 if sold commercially.
For a complete list of 1999 records, please visit 1999 Guinness Records in United States.