In 1976 Bill Koch was the surprise winner of America's first ever Olympic medal in the 30k cross country ski event. During his career he was known for many things: introducing skating on the World Cup scene and revolutionizing the sport, winning the first World Cup in 1982, winning a bronze medal at the 1982 World Championships, and carrying the American flag at the opening ceremony at the 1992 Olympics.
Less well known is the day in March 1981 when he went out to Marlboro Pond in Vermont, on a carefully groomed and measured loop with two USSA representatives as witnesses to break the 30K and 50k nordic world records, and all the running records from 800 meters to a marathon! His mile time was 3:20, and his 50k time was 1:59:47 which works out to 3:51 for each of the 31+ miles. (As an aside, his vision and way he went about all this, sort of makes the Nike 2-hour project look a bit overblown!)